"I don't care!"
Translation:Je m'en fiche !
I once encountered a phrase something like Je m'en cassé (I even forgot if there should even be an accent on cassé). Whatever that phrase is, I thought that means "I don't care", so instead of putting fiche as the last word, I selected cassée. Now I know it does not mean that, but what does je m'en cassé(e) mean now? Seriously. I have forgotten it!
I'm wondering about the level of rudeness implicit in the phrase "je m'en fiche." If your spouse asked you whether you would like tea or coffee, and if you wished to reply by saying "I don't care" (that is, "I don't care one way or the other; either option is acceptable to me"), would you say "je m'en fiche"? If not, what would be the polite way to express your reply in French?