Source : Webster's Revised Unabridged Dictionary (1913)

Gadwall \Gad"wall\, n. [Gad to walk about + well.] (Zo["o]l.)
   A large duck ({Anas strepera}), valued as a game bird, found
   in the northern parts of Europe and America; -- called also
   {gray duck}. [Written also {gaddwell}.]