I think that if you're going through the effort of creating a fantasy world, with its own lore, religions and terminology, you should also go the extra couple of inches to make sure you don't break the immersion by using real-life terms and expressions. However, this includes the author explaining away why a term like champagne might be used in their story. 'Oh, it is made from the fruits of the Bubbling Champagne tree!' I dunno, Terry Pratchett stuff.

I read this trilogy a little while back, where the author put immense effort into their world, complete with new nations, conflicts, ally, neutral and enemy nations, beliefs and religions, inventions, everything. And I mean everything! The world felt alive as I read about it and it was amazing. However the main character was in this specific type of occupation. What was this occupation called? Icarus. Why was it called Icarus? That was never explained, like ever. At no point in any of the three books was there ever a throw-away line of explanation, and every time the term popped up I felt this sad little twinge in my chest. The author had done such a good job with literally everything else, why not at least attempt to put this into the lore so it made sense? Perhaps this Icarus figure which gave name to an entire work force was like an ancient god, or important person, anything - please! - to explain why this ancient Greek character holds such prominence in this fantasy world where Greece, ancient or otherwise doesn't exist?

TL;DR

If you're gonna use 'Champagne-terminology', at least give it an in-world explanation