A.V.

late 14c., auctorisen, autorisen, "give formal approval or sanction to," also "confirm as authentic or true; regard (a book) as correct or trustworthy," from Old French autoriser, auctoriser "authorize, give authority to" (12c.) and directly from Medieval Latin auctorizare, from auctor (see author (n.)).

The meaning "give authority or legal power to" is from mid-15c. The modern spelling from late 16c. Related: Authorized; authorizing. Authorized Version as a popular name for the 1611 ("King James") English Bible is by 1811.