c. 1300, from Anglo-French tormentour, Old French tormenteor "torturer," agent noun from tormenter "to torture" (see torment (v.)).

late 14c., purseuere, "one who follows or chases with hostility, a persecutor or tormenter," agent noun from pursue.

c. 1300, "inflict torture on, distress," from Old French tormenter "torture, torment, oppress, agitate" (12c.), from Medieval Latin tormentare "to torment, to twist," from Latin tormentum "twisted cord, sling; clothes-press; instrument for hurling stones," also "instrument of torture, a rack," figuratively "anguish, pain, torment," from torquere "to twist" (from PIE root *terkw- "to twist"). Related: Tormented; tormenting.