From The Collaborative International Dictionary of English v.0.48 :
Coot \Coot\ (k[=oo]t), n. [Cf. D. koet, W. cwtair; cwta short, bodtailed + iar hen; cf. cwtau to dock. Cf. Cut.] 1. (Zool.) (a) A wading bird with lobate toes, of the genus Fulica. The common European or bald coot is Fulica atra (see under bald); the American is Fulica Americana. (b) The surf duck or scoter. In the United States all the species of ({[OE]demia are called coots. See Scoter. "As simple as a coot." --Halliwell. [1913 Webster] 2. A stupid fellow; a simpleton; as, a silly coot. [Colloq.] [1913 Webster]From WordNet (r) 3.0 (2006) :
coot n 1: slate-black slow-flying birds somewhat resembling ducks