What Say You to Anchovy Ketchup? :P
Ketchup has not always been made out of tomatoes. It started out as a general term for sauce, sometimes even made of mushrooms or fish brine with herbs and spices (mushroom ketchup is still available in some countries, btw.)
Some popular early main ingredients for the predecessor of ketchup include anchovy, oyster, lobster, walnut, kidney bean, cucumber, cranberry, lemon, and grape.