GADWALL, a word of obscure origin,  the common English name of the duck, called by Linnaeus Anas strepera, but considered by many modern ornithologists to require removal from the genus Anas to that of Chaulelasmus or Ctenorhynchus, of either of which it is almost the sole species. Its geographical distribution is almost identical with that of the common wild duck or mallard (see Duck), since it is found over the greater part of the northern hemisphere; but, save in India, where it is one of the most abundant species of duck during the cold weather, it is hardly anywhere so numerous, and both in the eastern parts of the United States and in the British Islands it is rather rare than otherwise. Its habits also, so far as they have been observed, greatly resemble those of the wild duck; but its appearance on the water is very different, its small head, flat back, elongated form and elevated stern rendering it recognizable by the fowler even at such a distance as hinders him from seeing its very distinct plumage. In coloration the two sexes appear almost equally sombre; but on closer inspection the drake exhibits a pencilled grey coloration and upper wing-coverts of a deep chestnut, which are almost wanting in his soberly clad partner. She closely resembles the female of the mallard in colour, but has, like her own male, some of the secondary quills of a pure white, presenting a patch of that colour which forms one of the most readily perceived distinctive characters of the species. The gadwall is a bird of some interest in England, since it is one of the few that have been induced, by the protection afforded them in certain localities, to resume the indigenous position they once filled, but had, through the draining and reclaiming of marshy lands, long since abandoned. In regard to the present species, this fact was due to the efforts of Andrew Fountaine, on whose property, in West Norfolk and its immediate neighbourhood, the gadwall, from 1850, annually bred in increasing numbers. It has been always esteemed one of the best of wild fowl for the table.
 The New English Dictionary has nothing to say. Webster gives the etymology gad well = go about well. Dr R.G. Latham suggested that it was taken from the syllables quedul, of the Lat. querquedula, a teal. The spelling "gadwall" seems to be first found in Willughby in 1676, and has been generally adopted by later writers; but Merrett, in 1667, has "gaddel" (Pinax rerum naturalium Britannicarum, p. 180), saying that it was so called by bird-dealers. The synonym "gray," given by Willughby and Ray, is doubtless derived from the general colour of the species, and has its analogue in the Icelandic Gráönd, applied almost indifferently, or with some distinguishing epithet, to the female of any of the freshwater ducks, and especially to both sexes of the present, in which, as stated in the text, there is comparatively little conspicuous difference of plumage in drake and duck.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)