Ketchup (or catsup) is a sauce or condiment, often made with tomatoes.
Larger tomato and ketchup
Ketchup has not always been made out of tomatoes. It started out as a general term for sauce, typically made of mushrooms or fish brine, herbs and spices. Later it was reformulated to include anchovies, walnuts, mushrooms and kidney beans. One popular theory is that the word ketchup is derived from the (茄汁) koechiap or ke-tsiap which is from the Amoy dialect of China by way of the Malay word, kechap. Around the late seventeenth century the name and samples arrived in England where it appeared in print as catchup and then finally as ketchup. A recipe for tomato ketchup found its way over the Atlantic and the rest is history. Ketchup in the 1800s referred to any sauce made with vinegar.
In 1981, Ronald Reagan's budget director, David Stockman, proposed classifying ketchup as a vegetable as part of Reagan's budget cuts for federally financed school lunch programs (it would make it cheaper to satisfy the requirements on vegetable content of lunches). The suggestion was widely ridiculed and the proposal was killed.
The basic recipe for modern ketchup is tomatoes, vinegar, sugar, salt, allspice, cloves and cinnamon. Onions, celery and other spices are frequent additions.