Yours, Etc.: Origins and Uses of 8 Sign-Offs
c.1200, throwe "pain, pang of childbirth, agony of death," possibly from Old English þrawan "twist, turn, writhe" (see throw), or altered from Old English þrea (genitive þrawe) "affliction, pang, evil, threat" (related to þrowian "to suffer"), from Proto-Germanic *thrawo (cf. Middle High German dro "threat," German drohen "to threaten"). Modern spelling first recorded 1610s. Related: Throes.