bittern (n.)

heron-like European bird, c. 1300, bitour, botor, from Old French butor "bittern," which is perhaps from Gallo-Roman *butitaurus, from Latin butionem "bittern" + taurus "bull" (see steer (n.)); according to Pliny, so called because of its booming voice, but this seems fanciful. Modern form from 1510s.