I had always thought that ketchup was tomato-based by definition. But no ... there was an origin story a few years back. Walnut ketchup was one of the early varieties, and liver ketchup was popular at one time.
A staple food designed for Toddlers. The proper method of eating is to lick and/or suck it off of french fries and then pushing the used french fry into their father's mouth. Not that I have any personal knowledge of it.