confess (v.) Look up confess at
late 14c., from Old French confesser (transitive and intransitive), from Vulgar Latin *confessare, from Latin confess-, past participle stem of confiteri "to acknowledge," from com- "together" (see com-) + fateri "to admit," akin to fari "speak," from PIE root *bha- (2) "to speak, tell, say" (see fame (n.)).

Its original religious sense was of one who avows his religion in spite of persecution or danger but does not suffer martyrdom. Old French confesser thus had a figurative sense of "to harm, hurt, make suffer." Related: Confessed; confessing. An Old English word for it was andettan.