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!
by dilary huff August 17, 2007