Yours, Etc.: Origins and Uses of 8 Sign-Offs
1580s, "to torture," from Middle French agoniser or directly from Medieval Latin agonizare, from Greek agonizesthai "to contend in the struggle" (see agony). Intransitive sense of "to suffer physical pain" is recorded from 1660s. That of "to worry intensely" is from 1853. Related: Agonized; agonizing.