"casse-toi !", as well as many offending expressions in French, uses regular language in a way that makes these phrases sound rude.
I think that "back off!" can also be rude, not so much because of the words themselves, but because of the context, because "Would you please step back a bit?" would be much nicer (Pourriez-vous reculer un peu, s'il vous plaît ?"
i was mistakenly interpreting it to mean "break in" as in "break in one's shoes" i guess from now on i shall go look up the verb on another site before trusting the hovering translation when it comes to idioms. lesson learned : ( thanks for the response and other translation though!
If you say "ma montre est cassée" it means that it no longer works.
If you say "j'ai cassé ma montre", it will mean that it is in pieces now.
"Briser" is more sophisticated and less usual than "casser".
A lot of fixed expressions use one or the other:
- he broke my heart = il m'a brisé le coeur
- to break the ice = briser la glace
- to break up a family/marriage = briser une famille/un mariage
- I feel like smashing everything up = j'ai envie de tout casser
- to spoil the atmosphere = casser l'ambiance