How did a fermented fish sauce become the red stuff on your fries?

Here’s the question worth chasing: how did a thin, salty, funky fish sauce brewed in southern China turn into the thick, sweet, tomato-red condiment squeezed onto billions of burgers every year? Because that’s the actual journey. The ketchup in your fridge shares a name with a sauce that had nothing to do with tomatoes, nothing to do with sweetness, and nothing to do with America.

Most people assume ketchup was always tomato-based. It wasn’t. For most of its recorded life, ketchup meant something closer to Worcestershire sauce: a dark, savory, umami-loaded liquid used to punch up gravies and fish dishes. The tomato showed up late. The sugar showed up later still.

The single most important thing to understand up front: ketchup is not a recipe that one person invented on one day. It’s a name that traveled the world and kept picking up new ingredients. Fermented fish in Asia. Mushrooms and walnuts in England. Tomatoes in America. Each region reached for whatever savory, funky, protein-rich stuff it had on hand, slapped the same word on it, and moved on.

So let’s trace it properly. Three distinct eras, one word connecting them, and a German American named Henry Heinz standing at the finish line.

The Asian fish-sauce roots and where the word actually comes from

Start with the name, because the name is the clearest thread running through the whole story. Food historians and linguists overwhelmingly agree that “ketchup” is Chinese in origin. The dominant theory, argued by Stanford linguist Dan Jurafsky among others, traces it to the Hokkien term often written as ke-tsiap, referring to a brine or sauce made from fermented fish.

You’ll see this spelled a dozen ways in the source material: ke-tsiap, koe-cheup, ge-thcup. That inconsistency isn’t sloppiness. It’s what happens when a spoken word from the Southern Min dialect gets transcribed by English, Dutch, and Portuguese traders who each heard it a little differently. Red Gold’s history of the condiment points to speakers of the Southern Min dialect in southern China using fermented fish paste and soybeans to make a sauce they called something like “ge-thcup” or “koe-cheup.”

There’s a competing story worth knowing about because it gets repeated a lot. A 1983 New York Times column claimed the word came from Cantonese “fan-kei cheop,” where fan-kei means tomato (“foreign vine-vegetable”) and cheop means juice. Drop the “fan” and you supposedly get “kei-cheop.” It’s a tidy story. It’s also almost certainly wrong. As Andrew F. Smith notes in Pure Ketchup: A History of America’s National Condiment, none of the early ketchup recipes had anything to do with the tomato, which knocks the legs out from under any etymology built on the word for tomato.

The same root word branched out across Southeast Asia. Epicurious traces it to Malaysian kicap manis and Indonesian kecap manis, a sweet soy sauce made with palm sugar or molasses that’s essential to dishes like satay, nasi goreng, and rendang. The “manis” means sweet. That Indonesian word, kecap, is a cousin of ketchup. Chinese traders and immigrants likely carried the concept there, and over time “ke-tsiap” softened into “kecap.”

What did this original sauce actually taste like? Thin. Dark. Salty. Deeply savory. Think fish sauce, not the sweet-sour goo we know now. It was a seasoning liquid, a way to add depth to a dish, and it was made by salting and fermenting fish or shellfish until they broke down into a pungent brine.

The origin of ketchup is Asian and savory, and the modern tomato version is a late offshoot, not the source. Hold onto that, because nearly every myth about ketchup collapses once you get the sequence right.

How the British got hold of it and made it weird

The British ran into this sauce through their colonial trade in South and Southeast Asia in the late 17th century. And they liked it. They liked it enough to try to make their own back home, which is where things get genuinely strange.

The first English reference to the word shows up in 1690, in a delightfully named book called A New Dictionary of the Terms Ancient and Modern of the Canting Crew, which defined “catchup” as “a high East-India sauce.” At the time “East India” meant South and Southeast Asia broadly. By 1711, in An Account of the Trade in India, Charles Lockyer wrote that “the best Ketchup” came from Tonqueen (in what’s now Vietnam) and that good versions were made and sold cheap in China.

Here’s the catch: hardly any British cooks had ever tasted the real thing. As Andrew F. Smith puts it in Pure Ketchup, “as few British sailors or colonial servants had actually traveled to Southeast Asia or sampled real ketchup, little need or inclination arose to duplicate the genuine ketchup, whatever that may have been.” So they didn’t recreate it. They improvised. They took the word and the general idea, a dark savory sauce, and built it from whatever was in the English larder.

The first published English ketchup recipe appears in Eliza Smith’s The Compleat Housewife in 1727. It’s a thin mixture of vinegar, white wine, anchovies, shallots, lemon peel, horseradish, and a fistful of spices, with a note that “the clear Liquor that comes from Mushrooms” could be added. Read that ingredient list again. It’s basically Worcestershire sauce before Worcestershire sauce existed.

From there the British went wild. Commercial versions settled into three main types:

One early recipe even used kidney beans as a base. Smith suspects that was a substitute for soybeans, since kidney beans were a recent import from North America. Nobody was chasing accuracy. They were chasing that dark, funky, umami hit.

Hannah Glasse’s hugely popular The Art of Cookery, Made Plain and Easy, first published in 1774, included two mushroom ketchup recipes with no fish at all. In one she suggests adding a pint of “mum,” a dark beer, so it will “taste like foreign catchup.” That line tells you everything: British cooks knew their version was an imitation, and they were still trying to chase the flavor of the imported original. In her other recipe she notes that some cooks add a whole head of garlic, then adds, dryly, “but I think that spoils it.”

Beer and wine, port, sherry, claret, added acidity and fermented funk to many of these sauces. Mace and clove were near-constant. These were catch-all flavor enhancers, ladled into gravies and over fish, not squeezed onto anything.

Even the spelling was a mess, and people knew it. The Domestic Chemist from 1831 counted three popular spellings and joked that these words “indicate a sauce, of which the name can be pronounced by every body, but spelled by nobody.” And notably, in 1831, that book still described ketchup as the product of “the liquefaction of salted mushrooms.” No tomatoes. We’re already 140 years past the word entering English and tomatoes still aren’t the default.

When the tomato took over and America made it sweet

So when did tomatoes crash the party? Early 1800s, in the United States, and it happened faster than you’d expect.

Tomatoes carried baggage in this era. Sometimes called “love apples,” they were eyed with suspicion in parts of Europe and America, partly because they belong to the nightshade family. But that fear faded, and by the late 18th century Americans were folding tomatoes into all kinds of dishes. Some early American recipes salted, strained, and spiced tomatoes into something recognizably ketchup-like.

The first published recipe for a tomato-based ketchup is widely credited to James Mease, a Philadelphia horticulturist, in 1812. His version was unstrained and lightly spiced, closer to a loose tomato sauce than the bottled stuff today. It included brandy but no vinegar, which meant it spoiled fast. Later cooks fixed that by adding vinegar and sometimes letting the tomatoes partially ferment, both of which fought spoilage and added tang.

Tomato ketchup caught on almost immediately. Smith writes that “whatever reason for the initial application of the term tomato ketchup, it was widely and swiftly adopted throughout America early in the nineteenth century.” But it didn’t wipe out the competition right away. Cookbooks through the 1800s kept printing dozens of recipes for mushroom, oyster, and walnut ketchups alongside the tomato version. For a good while, “ketchup” without a qualifier could still mean mushroom.

Two chemistry-driven changes turned early tomato ketchup into the modern product:

So the ketchup you know, thick, red, sweet, tangy, is a distinctly American 19th-century creation, and its defining sweetness didn’t lock in until the second half of that century. Early tomato ketchup was thinner, saltier, and far less sweet than what’s in the squeeze bottle now.

One quick clarification, since it comes up constantly. Catsup and ketchup are not two different foods. They’re two spellings of the same word, along with “catchup.” Which one a person uses tends to come down to region and habit. Both are correct. Even Heinz originally spelled it “catsup” on the label before “ketchup” won out.

The myths worth clearing up, including the medicine one

A few stubborn misconceptions deserve a direct correction, because they get repeated as fact all over the internet.

Myth: Ketchup was invented as a medicine. This one contains a grain of truth wrapped in a lot of exaggeration. In the 1830s, an Ohio physician named John Cook Bennett promoted tomatoes, and tomato ketchup, as a treatment for ailments like diarrhea and indigestion. His claims got turned into “tomato pills” that were marketed as cures. But ketchup did not originate as a medicine. It existed as a savory condiment for well over a century before anyone tried to sell it as a health tonic. The medicinal chapter was a brief, opportunistic marketing episode in America, not the reason ketchup was created.

Myth: Ketchup was always tomato-based. False, and it’s the most common mistake of all. For roughly the first century-plus of the word’s life in English, ketchup meant mushroom, fish, or walnut sauce. Tomatoes are the newcomer.

Myth: Ketchup is purely American. The modern mass-market bottle is deeply American, no argument. But the sauce’s DNA runs through China, Southeast Asia, and Britain first. Calling ketchup American is like calling pizza purely a New York invention. There’s truth in it, but you’re skipping most of the story.

Myth: One person invented ketchup. Nobody did. It evolved across centuries and continents. Even the tomato version, credited to James Mease in 1812 for the first published recipe, was riding on decades of earlier American experimentation with tomato-based sauces.

Myth: Catsup is an older or different food. No. Just a spelling variant. Same sauce.

And while we’re correcting things: early ketchup was not sweet. If you could taste a bottle of 18th-century mushroom ketchup, you’d probably describe it as sharp, salty, and boozy, not the dessert-adjacent condiment kids squeeze on everything today.

How Heinz standardized ketchup and won the bottle wars

Here’s where a scattered homemade sauce becomes a single dominant brand. In 1876, a first-generation German American named Henry J. Heinz launched his bottled ketchup, spelled “catsup” at the time. He’d already had success bottling grated horseradish, and ketchup fit his model: a shelf-stable, standardized product a busy household could just buy.

That word, standardized, is the whole point. Before Heinz, ketchup was a moving target. Every cookbook, every household, every small producer had its own recipe and its own idea of what ketchup even was. Heinz turned it into one consistent thing you could recognize, buy again, and trust. Brand historians generally credit Heinz as the company that transformed ketchup from a varied homemade sauce into a fixed commercial product.

Heinz made it thicker and sweeter than most rivals, closer to the profile Americans already craved. The famous “57 varieties” slogan on the label was, by most accounts, a number Henry Heinz simply liked the sound of. By 1900 the company was selling more than 60 products, so 57 was never a literal count.

Then there’s the bottle. The iconic slender glass Heinz bottle arrived in the early 20th century (the octagonal bottle is often dated to 1890). Popular lore connects the bottle’s design to ketchup’s thixotropic behavior, the physics fact that ketchup is thick at rest and flows when shaken or smacked. Anyone who has ever whacked the bottom of a glass bottle and gotten a sudden splorch on their plate has met thixotropy in person.

Heinz also fought a smart public-health battle. He aggressively promoted the fact that his ketchup contained no benzoate preservatives. Competitors leaned on those preservatives to mask shoddy tomatoes and lax factory sanitation and keep costs down. Heinz positioned his product as the clean, safe choice, and it worked. This was right as the pure-food movement was gaining steam in America, and Heinz rode that wave hard.

He won. Heinz came to dominate the ketchup market and has held that position ever since, even though plenty of excellent alternatives exist now. The reason your default mental image of ketchup is thick, sweet, deep red, and vaguely bottle-shaped is largely because Henry Heinz decided that’s what ketchup should be, then made everyone else’s version look like a compromise.

Ketchup around the world and the styles worth trying

The story doesn’t end at the American bottle. Ketchup kept mutating regionally, and some of those variations are worth knowing.

Different cultures put their own spin on it. Red Gold points to spicier, chutney-adjacent tomato condiments in India and to soy-based and fish-based ketchups still made across Southeast Asia, where the sauce’s fermented roots never fully left. In the Philippines, banana ketchup, made from mashed bananas dyed red, is a genuine staple born partly out of wartime tomato shortages. It’s sweeter and tangier and honestly delicious on fried chicken.

The condiment family tree ketchup spawned is enormous. Without tomato ketchup you lose the base of Russian and Thousand Island dressings, cocktail sauce, a lot of steak sauces, and Kansas City-style barbecue sauce. Ketchup is a foundational ingredient hiding inside a dozen other things you eat.

If the history has made you curious about what ketchup used to taste like, here’s a quick reference for the older and alternative styles, some of which you can still buy or make:

Modern tomato ketchup keeps evolving too. There are lower-sugar and lower-sodium versions for dietary needs, organic and all-natural lines made without artificial preservatives, and a whole category of gourmet and flavored ketchups: jalapeno, sriracha-spiked, and beyond. In a way this is the story coming full circle. Ketchup started as an ever-changing family of savory sauces made from whatever was around, and after a century of Heinz-enforced uniformity, it’s fragmenting into variety again.

The one thing to remember

If you forget every date and every cookbook and every spelling variant in here, remember this: ketchup did not start as tomato sauce. It started as a fermented fish sauce in China, traveled through Southeast Asia and Britain picking up mushrooms and walnuts along the way, and only became the thick, sweet, red condiment you know after Americans added tomatoes in the 1800s and Henry Heinz standardized it into a bottle. The tomato is the newest chapter, not the first. That single fact rearranges everything else you thought you knew about the red stuff on your fries.