'Duffle bag' is perhaps my worst instance of this (I use 'carryall bag' in most places where it or a similar term would appear, because 'duffle bag' dates back to only the early 20th century, its earliest known appearance in, of all things, an e. e. cummings poem), but the inverse is also troubling- I agonized over using the term 'x-ray' because it's such a weirdly specific OTL circumstance term that really shouldn't exist in most ATLs but there's simply no good, easily understood generic term or obvious alternate that wouldn't then require an extra half paragraph of explanation.
(I think, IIRC, the specific example we talked about was 'car'- I've preferenced 'auto' in a lot of stories, but no one will really notice if you don't say 'car' unless you draw attention to it.)
It's a really tough line to walk, because you can easily lose yourself in weeds forever in it- consider, for example, how many of the things you might say in a given day are a reference to an in-joke or a piece of media or any other thing that would be completely inexplicable to someone from an ATL, and then consider how rarely you see characters in any fiction, much less AH, reference popular media even obliquely (which would be difficult to explain in and of itself to a lot of premodern writers, where you need whole extra books to explain all the references present in the book you're reading).
Overall the best approach, I think, is to preference OTL terms where there's a good reason to, but if there's a simple and easy alternate term that would be instantly understandable, don't be afraid to use it, because you're the absolute god of the things that you're writing and no one can actually stop you from doing whatever you want except you.
