authoritative (adj.)

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). Meaning "having due authority, entitled to credence or obedience" is from 1650s; that of "proceeding from proper authority" is from 1809. Related: Authoritatively; authoritativeness.