"earlier," 1714, from Latin prior "former, previous, first;" figuratively "superior, better;" as a noun "forefather; superior rank;" comparative of Old Latin pri "before," from PIE *prai-, *prei-, from root *per- (1) "forward, through" (see per).

"superior officer of a religious house or order," late Old English, from Medieval Latin prior "superior officer," noun use of Latin adjective meaning "former, superior" (see prior, adj.). As short for prior arrest, by 1990, American English.