"wing joint, segment of a bird's wing" (technically the joint of a bird's wing furthest from the body), early 15c., from Old French pignon, penon "wing-feather, wing, pinion" (c. 1400), from Vulgar Latin *pinnionem (nominative *pinnio), augmentative of Latin pinna "wing" (from PIE root *pet- "to rush, to fly").
"small wheel with teeth to gear with a larger one" (as in rack and pinion), 1650s, from French pignon "pinion" (16c.), literally "a gable," from Old French pignon "pointed gable, summit," from Vulgar Latin *pinnionem, augmentative of Latin pinna "battlement, pinnacle" (see pin (n.)). Pinoun as "a gable" was borrowed from Old French in Middle English (late 13c.).
"disable by binding the arms," 1550s, older in English than literal sense "cut or bind the pinions (of a bird's wing) to prevent flying" (1570s); from pinion (n.1). Related: Pinioned.