c.1300, "an equal in civil standing or rank" (1215 in Anglo-L.), from Anglo-Fr. peir, O.Fr. per (10c.), from L. par "equal." Sense of "noble" (1382) is from Charlemagne's Twelve Peers in the old romances, like knights of the Round Table, originally so called because all were equal. Sociological sense of "one of the same age group or social set" is from 1944. Peerage first recorded 1454. Peer review is first recorded 1971.
1590s, variant of piren (late 14c.), with a long -i-, probably related to or from E. Fris. piren "to look," of uncertain origin. Influenced in form and sense by M.E. peren (late 14c.), aphetic form of aperen (see appear).