eider (n.)youdaoicibaDictYouDict
type of duck, 1743, from German Eider or Dutch eider, both from Old Norse æþar, genitive of æþr "duck," according to Watkins from a North Germanic root *athi-, from Proto-Germanic *ethi-, from PIE "probable root" *eti- "eider duck."
eiderdown (n.)youdaoicibaDictYouDict
"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.
eidetic (adj.)youdaoicibaDictYouDict
"pertaining to the faculty of projecting images," 1924, from German eidetisch, coined by German psychologist Erich Jaensch (1883-1940), from Greek eidetikos "pertaining to images," also "pertaining to knowledge," from eidesis "knowledge," from eidos "form, shape" (see -oid).