Yours, Etc.: Origins and Uses of 8 Sign-Offs
early 13c., from Old French conseillier (Modern French conseiller), from Latin consilator, agent noun from consiliare, from consilium (see counsel (v.)). Meaning "one who gives professional legal advice" is from 1530s. Psychological sense (marriage counsellor, etc., is from 1940).
an adviser (Prov. 11:14; 15:22), a king's state counsellor (2 Sam. 15:12). Used once of the Messiah (Isa. 9:6). In Mark 15:43, Luke 23:50, the word probably means a member of the Jewish Sanhedrim.