👉 The word you're looking for is "cryptic." Cryptic means difficult to understand or explain, so it's a playful and humorous way of describing this term.
Here's how your joke would sound: Cryptic: I'm trying to find an explanation for '45 freefont.conf.' But I can't seem to find one. Maybe we're on the right track if we go with 'cryptic' instead. "45 freefont.conf? How can you possibly explain such a complex document? It's like a cipher, but without the key. You get my drift?"