authority (n.)
c. 1200, autorite, auctorite "authoritative passage or statement, book or quotation that settles an argument, passage from Scripture," from Old French autorité, auctorité "authority, prestige, right, permission, dignity, gravity; the Scriptures" (12c.; Modern French autorité), from Latin auctoritatem (nominative auctoritas) "invention, advice, opinion, influence, command," from auctor "master, leader, author" (see author (n.)). Usually spelled with a -c- in English before 16c., when the letter was dropped in imitation of French, then with a -th-, probably by influence of authentic.

From c. 1300 in the general sense "legal validity," also "authoritative book; authoritative doctrine" (opposed to reason or experience); "author whose statements are regarded as correct." From mid-14c. as "right to rule or command, power to enforce obedience, power or right to command or act." In Middle English also "power derived from good reputation; power to convince people, capacity for inspiring trust." From c. 1400 as "official sanction, authorization." Meaning "persons in authority" is from 1610s; Authorities "those in charge, those with police powers" is recorded from mid-19c.