WTW for when there is a fairly straightforward concept that doesn't have a word to describe it?

I don't know if this is too meta, but after being on r/whatstheword for a while, that's what I've been wondering. Language evolves constantly, so really anything could have its own word. But in a world of infinite possibilities, there is of course a chance for any number of things that don't have a word yet.

I think there should probably be a word for something that doesn't have its own word yet.

Also, as an afterthought, I think there's a difference between things that could have a word already, but they just happen to not be named yet, the unknown, on the one hand - and things that are fundamentally unknowable and cannot have a word, on the other hand.

So, the former group could probably have a name.

I don't mean ineffable, that's probably the second group. I don't mean untranslatable, because that assumes that there is a language that has a word for it already.

I'm thinking, when there is a new word, that's a neologism. But what's it called when the neologism hasn't been proposed yet?