c. 1300, "an equal in rank, character, or status" (early 13c. in Anglo-Latin), from Anglo-French peir, Old French per (10c.), from Latin par "equal" (see par (n.)). Sense of "a nobleman of especial dignity" (late 14c.) is from Charlemagne's Twelve Peers in the old romances, who, like the Arthurian knights of the Round Table, originally were so called because all were equal. Sociological sense of "one of the same age group or social set" is from 1944. Peer review "evaluation of a scientific project by experts in the relevant field" is attested by 1970. Peer pressure is recorded by 1971.
late 14c., "degrade socially" (for marrying below rank or without proper ceremony), from Anglo-French and Old French desparagier (Modern French déparager) "reduce in rank, degrade, devalue, depreciate," originally "to marry unequally, marry to one of inferior condition or rank," and thus, by extension, to bring on oneself or one's family the disgrace or dishonor involved in this, from des- "away" (see dis-) + parage "rank, lineage" (see peer (n.)).
Also from late 14c. as "injure or dishonor by a comparison," especially by treating as equal or inferior to what is of less dignity, importance, or value. Sense of "belittle, undervalue, criticize or censure unjustly" is by 1530s. Related: Disparaged; disparaging; disparagingly.
"look inquisitively, look closely or with scrutinizing curiosity," c. 1300, prien "to peer in," a word of unknown origin, perhaps related to late Old English bepriwan "to wink." Related: Pried; prying. As a noun, "act of prying, curious or close inspection," from 1750; meaning "inquisitive, intrusive person" is from 1845.