Ketchup comes from the Hokkien Chinese word, kê-tsiap, the name of a sauce derived from fermented fish. It is believed that traders brought fish sauce from Vietnam to southeastern China.
The British likely encountered ketchup in Southeast Asia, returned home, and tried to replicate the fermented dark sauce. This probably happened in the late 17th and early 18th centuries as evidenced by a recipe published in 1732 for “Ketchup in Paste,” by Richard Bradley, which referenced “Bencoulin in the East-Indies” as its origin. (See “
How a Food Becomes Famous.”)
But this was certainly
not the ketchup we would recognize today. Most British recipes called for ingredients like mushrooms, walnuts, oysters, or anchovies in an effort to reproduce the savory tastes first encountered in Asia. Mushroom ketchup was even a purported favorite of Jane Austen. These early ketchups were mostly thin and dark, and were often added to soups, sauces, meat and fish. At this point, ketchup lacked one important ingredient.
Enter the tomato. The first known published tomato ketchup recipe appeared in 1812, written by scientist and horticulturalist, James Mease, who referred to tomatoes as “love apples.” His recipe contained tomato pulp, spices, and brandy but lacked vinegar and sugar.
https://www.nationalgeographic.com/...he-plate/2014/04/21/how-was-ketchup-invented/