early 15c., advertisen, "to take notice of" (a sense now obsolete), from Old French advertiss-, present-participle stem of advertir (earlier avertir) "make aware, call attention, remark; turn, turn to" (12c.), from Latin advertere "to direct one's attention to; give heed," literally "to turn toward," from ad "to, toward" (see ad-) + vertere "to turn" (see versus).
The transitive sense of "give notice to others, inform, warn; make clear or manifest" (mid-15c.) is by influence of advertisement; the specific commercial meaning "call attention to goods for sale, rewards, etc." emerged by late 18c. Compare advert (v.) "turn (someone's) attention to." Related: Advertised; advertising.