Ke-tsiap — a spicy pickled-fish condiment popular in 17th-century China — is said to be the origin of the name "ketchup. " British seamen brought the ke-tsiap home and throughout the years the formula was changed to contain anything from nuts to mushrooms. It wasn't until the late 1700s that canny New Englanders added tomatoes to the blend and it became what we know today as ketchup. Also called catsup and catchup, this thick, spicy sauce is a traditional American accompaniment for French-fried potatoes, hamburgers and many other foods. Ketchup usually has a tomato foundation, though gourmet markets often carry condiments with similar appellations that might have a base of anything from walnuts to mangoes to mushrooms. Vinegar gives ketchup its tang, while sugar, salt and spices contribute to the blend. In addition to being used as a condiment, ketchup is used as an ingredient in many dishes.