teal (n.)

c. 1300, tele, "small freshwater duck," a word of uncertain origin, perhaps from an unrecorded Old English word cognate with Middle Dutch teling "teal," Middle Low German telink, from West Germanic *taili.

As the name of a shade of dark greenish-blue resembling the color patterns on the fowl's head and wings, it is attested from 1923 in clothing advertisements.