Scroll down to the bottom of the article, there’s an 18th-century recipe for “mushroom ketchup.” (Along with a video on how to make it: https://www.youtube.com/watch?v=29u_FejNuks)

Be interesting to see how close it is to your wife’s modern version!

The word originates from eastern China (Xiamen or previously know as Amoy), the Minnan-hua language uses kôe-chiap or kê-chiap. Originally a sauce of pickled fish with spices.

It's one several theories, apparently - https://en.wikipedia.org/wiki/Ketchup#Etymology

Yes, interesting. I think there was an active spice trading route from Japan through Xiamen hundreds of years ago. Perhaps a true international product.

According to this post...

But who came up with the word “Ketchup”?

Who knows? There’s much debate over the origin of this word. Some say it’s a variant of a Chinese word for fish sauce. Others say it is a Malay word for the same.

In India (I first encountered it in Kenya), there's kachumbari, a kinda simple chutney of diced tomatoes and onion. I always wondered if that was the origin...

That's interesting, but I was talking about variations of tomato ketchup. The ketchup in Germany, the UK, and the US are all very different. I didn't like the ketchup in Germany at all (and I don't mean the curry ketchup...).

Probably less sugar than American ketchup... I vaguely recall the ketchup in Germany (non curry) having more vinegar too.