Hmm, I don't get a hit for "slugulus" or "eructo" (case insensitive) in any of the 7. Interestingly two mentions of "vomit" are in book 6, but neither in reference to to slugs (plenty of Slughorn of course!). Book 5 was the only other one a related hit came up:

> Ron nodded but did not speak. Harry was reminded forcibly of the time that Ron had accidentally put a slug-vomiting charm on himself. He looked just as pale and sweaty as he had done then, not to mention as reluctant to open his mouth.

There could be something with regional variants but I'm doubtful as the Fandom site uses LEGO Harry Potter: Years 1-4 as the citation of the spell instead of a book.

Maybe the real LLM is the universe and we're figuring this out for someone on Slacker News a level up!