Meaning

noun an admission of misdeeds or faults

noun a written document acknowledging an offense and signed by the guilty party

noun (Roman Catholic Church) the act of a penitent disclosing his sinfulness before a priest in the sacrament of penance in the hope of absolution

originFrom Middle English confessioun, from Old French confession, from Latin cōnfessiō, cōnfessiōnem (“confession, acknowledgment, creed or avowal of one's faith”). Displaced native Old English andetnes. Doublet of confessio. Morphologically confess + -ion. Sense 6 is a calque of 告白 (kokuhaku).

Etymology from Wiktionary, CC BY-SA 3.0