The neologism that never was

There is of course a long list, an uncompilable list (because the rules are different for everyone, because everyone has to write their own) of Words That Can't Be Used In Fantasy. They're modern constructs, or they're eponyms taken from the names of people or places that don't exist in this particular fantasy world (alas! no sodomy, ever!), or whatever.

I just thought I'd hit another one. I have people trekking through rainforest, and I wanted a word for that kind of rain that is barely more than a fine suspension of water in air; and of course I have the word, and it is mizzle. Which I thought I couldn't use, because I've always understood it to be a recent concoction, a jocular admixture of mist and drizzle.

I looked it up, though, just to be sure of my disappointment - and no! How wrong I was! We have it via the Low German - miseln, mist - and it is a perfectly proper word, and technically I can use it without further hesitation.

Please to note that 'technically' - because the problem, of course, is that if I thought it was a modern invention, chances are that other people will too, and if I use it they will trip over it anyway, rightly or wrongly, and so fall out of the story for a moment, which is of course the reason why I thought I couldn't use it in the first place...