By TrivBits, Staff Writer — Published August 23, 2026

Table of Contents

• Key Takeaways
• The Fascinating Origins: When Ketchup Meant Fish Sauce
• The Western Experiments: Mushrooms, Walnuts, and Oysters
• The Tomato Revolution: How America Changed Everything
• From Fermented Fish to Bottled Perfection
• The Linguistic Journey: How a Word Survived Its Meaning
• Frequently Asked Questions
• Sources

Did you know that the ketchup sitting in your refrigerator has almost nothing in common with its original ancestor? This surprising truth reveals one of the most interesting food transformations in culinary history. The secret behind ketchup’s evolution starts not with tomatoes, but with fermented fish guts and brine from Southeast Asia. What we now consider America’s favorite condiment began as a pungent, savory sauce that would be nearly unrecognizable to modern palates.

The journey from fish sauce to tomato-based condiment spans centuries and continents, involving Chinese traders, British colonists, and American innovators. This is a story of adaptation, commerce, and how a single word can survive while its meaning transforms completely.

Key Takeaways

• Original ketchup was a fermented fish sauce called “kê-tsiap” or “kôe-chiap” from Southeast Asia, containing no tomatoes whatsoever.
• British sailors encountered this sauce in the 17th century and brought the concept back to Europe, where cooks tried recreating it with local ingredients.
• Early Western ketchup recipes used mushrooms, walnuts, oysters, and anchovies—anything but tomatoes.
• Tomatoes didn’t become the primary ketchup ingredient until the early 19th century in America.
• The shift to tomato ketchup solved preservation problems and created the sweet, tangy condiment we know today.
• Modern ketchup bears virtually no resemblance to its fermented fish ancestor except in name.

The Fascinating Origins: When Ketchup Meant Fish Sauce

The secret behind ketchup’s fish-based origins lies in the coastal communities of southern China and what is now Vietnam and Indonesia. Local populations developed fermented fish sauces as a way to preserve their catches and create concentrated flavor enhancers. These sauces, known by various names including “kê-tsiap” in the Hokkien Chinese dialect, combined salted fish with the liquid that resulted from fermentation.

The process was simple but time-intensive. Fish and salt mixed together would break down over weeks or months, creating a dark, intensely flavored liquid. This wasn’t a condiment you’d squeeze on fries. It was a cooking ingredient, used sparingly to add umami depth to dishes.

British sailors and traders encountered these fish sauces during their voyages to Southeast Asia in the 1600s and 1700s. They loved the complex, savory punch it gave to their meals. But there was a problem: fish sauce didn’t travel well on long sea voyages, and once back in England, the ingredients weren’t readily available.

The Western Experiments: Mushrooms, Walnuts, and Oysters

British cooks became obsessed with recreating the exotic sauce they’d heard about from returning sailors. Without access to the original ingredients or methods, they improvised wildly. Cookbooks from the 18th century reveal the creativity—and confusion—surrounding ketchup recipes.

Mushroom ketchup became particularly popular in England. Cooks would salt mushrooms, extract their liquid, then boil it down with spices like cloves, ginger, and pepper. The result was a dark, savory sauce that bore some resemblance to the original Asian fish sauces in color and umami intensity.

Other recipes called for walnuts, which produced a brown, tangy sauce. Some used oysters or anchovies, getting closer to the original fish-based concept. Each household had its own version, and “ketchup” became a catch-all term for any spiced, preserved sauce used to season food.

What united these recipes wasn’t their ingredients but their purpose: to capture that elusive savory quality that made food more delicious. The word “ketchup” had become divorced from any specific ingredient, referring instead to a category of condiments.

The Tomato Revolution: How America Changed Everything

Tomatoes entered the ketchup story surprisingly late. For much of history, Europeans viewed tomatoes with suspicion, believing them poisonous because of their relation to deadly nightshade. This myth persisted well into the 1700s.

American cooks in the early 1800s began experimenting with tomato-based ketchup recipes. The exact origins are murky, but by the 1810s and 1820s, recipes for tomato ketchup appeared in American cookbooks. These early versions were spicier and less sweet than modern ketchup, often containing ingredients like cayenne pepper, cloves, and allspice.

The tomato version solved several problems. Tomatoes were abundant in America during summer and early fall. The fruit’s natural acidity helped with preservation. And the resulting sauce had a pleasant, versatile flavor that appealed to American tastes.

But early tomato ketchup had a major flaw: it spoiled quickly. Without proper preservation techniques, bottles would ferment, spoil, or even explode. Some manufacturers added coal tar or other dubious preservatives. The condiment had a somewhat dangerous reputation.

From Fermented Fish to Bottled Perfection

The transformation into modern ketchup required solving the preservation problem. By the late 1800s, manufacturers discovered that using ripe tomatoes, increasing vinegar content, and adding sugar created a stable product that could sit on shelves for months.

The H.J. Heinz Company, founded in the 1860s, perfected the formula and marketing of tomato ketchup. Their version was thicker, sweeter, and more consistent than competitors. The clear glass bottle showcased the product’s purity at a time when food safety was a genuine concern.

This commercial success cemented tomato ketchup as the default meaning of the word. Within a generation or two, most people forgot that ketchup had ever meant anything else. The fish sauce origins became a curious historical footnote.

The Linguistic Journey: How a Word Survived Its Meaning

Few words have traveled as far—both geographically and semantically—as “ketchup.” The term likely derives from Hokkien Chinese, though the exact etymology remains debated among linguists. What’s remarkable is that the word persisted even as the thing it described changed completely.

This linguistic survival happened because “ketchup” never referred to specific ingredients. It described a concept: a flavorful, preserved sauce that enhanced other foods. As long as something fit that broad definition, it could be called ketchup.

The spelling also evolved. You’ll find “catsup” and “catchup” in historical documents, reflecting different attempts to render foreign sounds in English. These variations coexisted for centuries before “ketchup” became the dominant spelling in the 20th century.

Frequently Asked Questions

Was original ketchup really made from fish?

Yes, the earliest versions of what became known as ketchup were fermented fish sauces from Southeast Asia and southern China. These sauces combined salted fish with the liquid produced during fermentation, creating an intensely savory condiment similar to modern fish sauce or soy sauce. The word “ketchup” comes from terms used to describe these fish-based sauces.

When did tomatoes become the main ingredient in ketchup?

Tomato-based ketchup emerged in America during the early 1800s, with recipes appearing in cookbooks by the 1810s and 1820s. However, tomato ketchup didn’t dominate the market until the late 1800s, when manufacturers solved preservation problems and began mass-producing the condiment. Before that, mushroom and walnut ketchups were equally common in Western kitchens.

Can you still buy fish-based ketchup today?

While you won’t find fish ketchup labeled as such, the original concept lives on in Asian fish sauces like Vietnamese nuoc mam or Thai nam pla. These products are direct descendants of the fermented fish sauces that inspired the word “ketchup.” Some specialty food companies have also created modern interpretations of historical ketchup recipes, including mushroom and walnut varieties.

Why did ketchup change from fish sauce to tomato sauce?

The transformation happened because Western cooks couldn’t easily replicate the original Asian fish sauces and experimented with local ingredients instead. Tomatoes eventually won out in America because they were abundant, naturally acidic for preservation, and produced a flavor that appealed to American palates. Commercial success and effective marketing by companies like Heinz then standardized tomato ketchup as the norm.

Next time you squeeze ketchup onto your burger, remember you’re participating in a culinary tradition that spans continents and centuries. That familiar red sauce connects you to Chinese fish fermenters, British mushroom experimenters, and American tomato innovators—all linked by a single word that refused to die even as everything it described transformed beyond recognition.

Sources

• Smithsonian Magazine – Food History
• Encyclopedia Britannica – Ketchup
• National Geographic – Culinary History