"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.
1. The only way out was that he covered with eiderdown quilts and I with silk - padded ones.
2. Silk and eiderdown make a perfect match in a comforter.