break one's ass
Also, break or bust one's ass or balls or butt or chops.
Exert oneself to the utmost, try extremely hard, as in I've been breaking my ass to finish early. This expression is considered vulgar slang; both ass, for backside or buttocks, and balls, for male genitals, are rude; butt, for buttocks, and chops, for either the mouth or the legs, are informal and emphatic but not quite as offensive. For a more polite synonym, see break one's back. [Slang; first half of 1900s]
break someone's ass. Also, . Thrash or harass someone, as in Jim threatened to break Tim's ass, or The boss broke his workers' chops to improve service. [Vulgar slang; mid-1900s]