[throwaway98700k]

It’s as common as je ne sais quoi or deja vu or ennui.

This one’s on you. Here’s a helpful list: https://en.m.wikipedia.org/wiki/Glossary_of_French_expressio...

[celtain]

It's definitely not as common as deja vu.

[awb]

I’ve heard those other ones a ton of times.