Ketchup, which is also called catsup, is a table sauce, traditionally of various flavors, notably mushroom, oyster and walnut, but in modern times the term without modification usually means tomato ketchup, sometimes called tomato sauce, or red sauce.
It is a sweet and tangy sauce, typically made from tomatoes, vinegar, a sweetener, and assorted seasonings and spices.
The sweetener is most commonly sugar or high fructose corn syrup. Seasonings vary from recipe to recipe, but commonly include onions, allspice, cloves, cinnamon, garlic, and celery.
Tomato ketchup is often used as a condiment with various dishes that are usually served hot, including french fries, hamburgers, sandwiches, hot dogs, eggs, and grilled or fried meat. Ketchup is sometimes used as a basis or ingredient for other sauces and dressings. Mushroom ketchup is widely available in the UK.
In the 17th century the Chinese mixed a concoction of pickled fish and spices and called it kôe-chiap or kê-chiap meaning the brine of pickled fish or shellfish.
By the early 18th century, the table sauce had made it to the Malay states where it was discovered by English explorers. The Indonesian-Malay word for the sauce was kecap (pronounced “kay-chap”). That word evolved into the English word “ketchup”. English settlers took ketchup with them to the American colonies.