I have just been reading a most amusing section in the 1950s guide to modern manners about using and pronouncing 'foreign words'.
This refers to what I can only assume was 'de rigueur' at the time, substituting French phrases into everyday English. These are referred to in the text as 'foreign' words but in fact all those cited are French!
"Today no one thinks any less of a person who employs no foreign expressions at all, and if she uses a foreign one where an English one is just a explicit, she is liable to be thought a trifle affected...."
"Even more disconcerting are the French words you may meet in conversation, especially since a good many of these have acquired a slang meaning which often has little in common with the dictionary one"
What is then interesting is that the list of 'foreign' (i.e. French) phrases that they give as examples are so much part of everyday language now that I would imagine that few people would identify them as 'foreign' at all!
(Such as ambiance, banal, bouquet, buffet, clique, corsage, de luxe, elite, entourage, finesse, foyer, gaffe, penchant...)