There are a lot of basic, common words that don't fit in a non-Earth setting. For example, I had one character say "the heavens", just referring to up. Well, this is an alternate world. There's no bible, there's no Jesus, there's no angels, there's no Judeo-Christian God. So there's no such concept as heaven.
Or if you've got a character who's paralyzed who's in kind of a steampunk wheelchair. Except, would they use the word 'wheelchair'? It seems like that's culturally dependent.
And then I heard that Mary Robinette Kowal made a custom dictionary out of all of Jane Austen's writing for her regency novels, to make sure she didn't use a word that was out of place.
So my question is, hasn't anyone ever done this for medieval fantasy? Seems like it's a no-brainer, with some constant mistakes writers do. Or at least, maybe we can crowd-source a list?