Old English feðer "feather," in plural, "wings," from Proto-Germanic *fethro (cf. Old Saxon fethara, Old Norse fioþr, Swedish fjäder, Middle Dutch vedere, Dutch veder, Old High German fedara, German Feder), from PIE *pet-ra-, from root *pet- "to rush, to fly" (see petition (n.)). Feather-headed "silly" is from 1640s. Feather duster attested by 1858. Figurative use of feather in (one's) cap attested by 1734.