Hm, it seems like there ought to be a page for that particular scenario, because it seems familiar (“Ah! It's an X!” “sigh, It's not an X. It's a YZW.”). The closest matches I've found are Not Using The Z Word, and Our Vampires Are Different ⊂ Our Monsters Are Different, but neither of them are about the characters doing the naming.

(But none of this is about “nearest cliche” as covered in the post; I did my research based off your comment, before I read the post.)