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.)).
It usually was spelled with a -c- in English before 16c. but the letter was dropped in imitation of French, then with a -th-, probably by influence of authentic.
It is attested from c. 1300 in the general sense of "legal validity," also "authoritative doctrine" (opposed to reason or experience), also "author whose statements are regarded as correct." It is from mid-14c. as "right to rule or command, power to enforce obedience, power or right to command or act."
In Middle English it also meant "power derived from good reputation; power to convince people, capacity for inspiring trust." It is attested from c. 1400 as "official sanction, authorization." The meaning "persons in authority" is from 1610s; the authorities "those in charge, those with police powers" is recorded from mid-19c.
"power, authority, supernatural power," 1843, from Maori, "power, authority, supernatural power."
c. 1600, "dictatorial" (a sense now restricted to authoritarian), earlier auctoritative (implied in auctoritativeli "with official approval or sanction"), from Medieval Latin auctoritativus, from Latin auctoritatem (see authority).
The meaning "having due authority, entitled to credence or obedience" is from 1650s; that of "proceeding from proper authority" is from 1809. Related: Authoritatively; authoritativeness.
"authority to command the national military forces," in extended use "an empire," 1650s, from Latin imperium "command, supreme authority, power" (see empire). Hence Latin phrase imperium in imperio "a state within a state."