Counselor
Middle English (in the general sense ‘adviser’): from Old French conseiller, from Latin consiliarius, and Old French conseillour, from Latin consiliator, both from consilium ‘consultation or advice’.
wiktionary
From Old French conseillier, from Latin consiliator, agent noun from cōnsilior(“I take counsel”), from cōnsilium(“plan, council, wisdom, advice”). Compare councilor.
etymonline
counselor (n.)
mid-13c., counseiler, "one who gives counsel or advice, a confidante," from Old French conseillier "counselor, adviser" (Modern French conseiller), from Latin consilator, agent noun from consiliare, from consilium (see counsel (v.)).
Also sometimes counsellor, but the double -l- is unetymological and perhaps is modeled on chancellor. Meaning "one who gives professional legal advice, a counseling lawyer," is from 1530s. Psychological sense (as in marriage counselor, is from 1940).
