smew 
(smy)
(smy)n.
A small Eurasian diving duck (Mergellus albellus), the male of which has white and black plumage and a white crest.
[Perhaps akin to earlier and dialectal English smee, any of various duck species; akin to German dialectal schmei-, schmü- (in Schmeiente, Schmünte, widgeon : schmei-, schmü- + German Ente, duck), and to Dutch smient.]