eiderdown (n.)youdaoicibaDictYouDict[eiderdown 词源字典]
"soft feathers of the eider-duck" (such as it uses to line its nest), 1774; see eider + down (n.1). Ultimately from Icelandic æðardun, via a Scandinavian source (compare Danish ederdunn) or German Eiderdon.[eiderdown etymology, eiderdown origin, 英语词源]