fightin' words
An insult or insults that are sufficiently offensive to the insulted person that he/she becomes angry enough to start throwing punches.
Person 1: Too bad your mama didn't drown you when you were born, you worthless nigger/kike/camel jockey/bitch/cracker/gook/insert chosen offensive word(s) here!
Person 2: I'm gonna beat your ass! Them's fightin' words!
Person 2: I'm gonna beat your ass! Them's fightin' words!
fightin' words
words that are designed to or are capable of provoking violence
It's one thing to argue, but these ar fightin' words
them's fightin' words
An old-time expression interjected after one is on the receiving end of a harsh criticism. A fight will usually occur as a result.
Northerner: You're a dumbass from the south, and so is your slave beating mother.
Southerner: (draws gun) Them's fightin' words!
Southerner: (draws gun) Them's fightin' words!