felon: [13] Medieval Latin fellō (a word of uncertain origin, sometimes referred to Latin fel ‘gall, poison’) meant ‘evil-doer’. Its nominative form gave English the adjective fell ‘fierce, lethal’, via Old French fel, while its stem form, fellōn-, passed into English through Old French felon. The derivative felony [13] comes from Old French felonie. => fell[felon etymology, felon origin, 英语词源]