late 12c., "person who speaks for God; one who foretells, inspired preacher," from Old French prophete, profete "prophet, soothsayer" (11c., Modern French prophète) and directly from Latin propheta, from Greek prophetes (Doric prophatas) "an interpreter, spokesman," especially of the gods, "inspired preacher or teacher," from pro "before" (from PIE root *per- (1) "forward," hence "in front of, before") + root of phanai "to speak," from PIE root *bha- (2) "to speak, tell, say."
The Greek word was used in Septuagint for Hebrew nabj "soothsayer." Early Latin writers translated Greek prophetes with Latin vates, but the Latinized form propheta predominated in post-Classical times, chiefly due to Christian writers, probably because of pagan associations of vates. In English, meaning "prophetic writer of the Old Testament" is from late 14c. Non-religious sense is from 1848; used of Muhammad from 1610s (translating Arabic al-nabiy, and sometimes also al-rasul, properly "the messenger"). The Latin word is glossed in Old English by witga.