These are the sorts of things that won't yield to a
specific keyword search (because you aren't giving the search engine the "terms of art" used people who use the thing), but where you can probably figure these out pretty quickly if you just do a search to find some kind of index for the category-of-thing and start browsing.
I'd recommend search queries like "types of knives", "obscure kitchen utensils", "what is this knife", etc.
You can also try giving /r/tipofmytongue or a related subreddit a very detailed description of the object. Some of the results from the above queries point to people asking questions like this on subreddits like /r/tools.
(Or you could do the same thing with ChatGPT — but that'll only work if someone has ever before described the object in a book or on the Internet somewhere, in the terms you're using. ChatGPT can only match your verbal questions to verbal memories. Whereas a person on a subreddit can take your description, conjure a mental image of it, and then correlate that mental image with a visual memory.)
I'll also take a shot at giving you starting points, just because I happen to find learning about weird kitchen tools fascinating:
> Like a ridiculously long knife with a slightly curved blade, rounded tip, and blunt edge.
A cake-icing spatula of some kind? I would imagine one made specifically for smoothing the icing on the side of a cylindrical layer cake would have this shape.
Usually cake spatulas are also offset (blade makes two complementary bends and so ends up parallel to, but not in line with, the handle), but they don't have to be.
> Or a serrated knife with that curves back on itself.
If the end can also be used as a fork, then that's a cheese knife.