The three extant species all breed in the cooler latitudes of the Northern Hemisphere.

[3] The genus Somateria was introduced in 1819 to accommodate the king eider by the English zoologist William Leach in an appendix to John Ross's account of his voyage to look for the Northwest Passage.

[4][5] The name is derived from Ancient Greek σῶμα : sōma "body" (stem somat-) and ἔριον : erion "wool", referring to eiderdown.

Two undescribed species are known from fossils, one from Middle Oligocene rocks in Kazakhstan and another from the Late Miocene or Early Pliocene of Lee Creek Mine, United States.

The Barrow Duck-In, a 1961 protest against game preservation laws in Alaska, when many eider ducks were shot out-of-season to provoke mass arrests.