Yours, Etc.: Origins and Uses of 8 Sign-Offs
late 14c., from Old French hainos "inconvenient, awkward; hateful, unpleasant; odious" (Modern French haineux), from haine "hatred," from hair "to hate," from Frankish *hatjan (cf. Old Saxon haton, Old English hatian "to hate;" see hate (v.)). Related: Heinously; heinousness.