Anyone who has multiple common languages with a friend knows this well. It’s quite common to drop a word from a different language into the middle of a sentence even when the sentence’s language has a word for it, just because there can be meaningful nuance or partition that the speaker wants to convey.
Strangely, doctrine in the US seems to be that one shouldn’t mix languages in a sentence when speaking to children. Somehow it will confuse them. Yet I’ve never seen anyone manage that in a polyglot household with kids.