- fanatic
- 1520s, "insane person," from L. fanaticus "mad, enthusiastic, inspired by a god," originally, "pertaining to a temple," from fanum "temple," related to festus "festive" (see feast). Current sense of "extremely zealous," especially in religion, is first attested 1640s. The noun is from mid-17c., originally in religious sense, of Nonconformists.
"A fanatic is someone who can't change his mind and won't change the subject." [Winston Churchill]