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