pinion (1) Look up pinion at Dictionary.com
"wing joint," c.1440, from M.Fr. pignon (c.1400), from V.L. *pinnionem, from L. penna "wing" (see pen (1)). Verb meaning "disable by binding the arms" is from 1558, older than lit. sense "cut the pinions of a wing to prevent a bird from flying" (1577).
pinion (2) Look up pinion at Dictionary.com
"small gear with teeth" (as in rack and pinion), 1659, from Fr. pignon, from O.Fr. pignon "crenellation, battlement," aug. of L. pinna "battlement, pinnacle;" confused with (but perhaps ult. a variant of) penna "wing, feather, peak" (see pen (1)).