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.
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.
mid-14c., auctor, autour, autor "father, creator, one who brings about, one who makes or creates" someone or something, from Old French auctor, acteor "author, originator, creator, instigator" (12c., Modern French auteur) and directly from Latin auctor "promoter, producer, father, progenitor; builder, founder; trustworthy writer, authority; historian; performer, doer; responsible person, teacher," literally "one who causes to grow," agent noun from auctus, past participle of augere "to increase" (from PIE root *aug- (1) "to increase").
From late 14c. as "a writer, one who sets forth written statements, original composer of a writing" (as distinguished from a compiler, translator, copyist, etc.). Also from late 14c. as "source of authoritative information or opinion," which is now archaic but is the sense behind authority, etc.
In Middle English the word sometimes was confused with actor. The -t- changed to -th- 16c., on the model of a change in Medieval Latin which was made on the mistaken assumption of a Greek origin and from confusion with authentic.
...[W]riting means revealing oneself to excess .... This is why one can never be alone enough when one writes, why even night is not night enough. ... I have often thought that the best mode of life for me would be to sit in the innermost room of a spacious locked cellar with my writing things and a lamp. Food would be brought and always put down far away from my room, outside the cellar's outermost door. The walk to my food, in my dressing gown, through the vaulted cellars, would be my only exercise. I would then return to my table, eat slowly and with deliberation, then start writing again at once. And how I would write! From what depths I would drag it up! [Franz Kafka, "Letters to Felice," 1913]
"power, authority, supernatural power," 1843, from Maori, "power, authority, supernatural power."
"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."