bittern: [14] The Latin word for ‘bittern’ (a marsh bird) was būtiō, but by the time it reached Old French it had become butor. The discrepancy has been accounted for by proposing a Vulgar Latin intermediate *būtitaurus, literally ‘bittern-bull’ (Latin taurus is ‘bull’), coined on the basis of the bittern’s loud booming call, supposedly reminiscent of a bull’s. The original English forms, as borrowed from Old French, were botor and bitoure; the final -n first appeared in the 16th century, perhaps on the analogy of heron.
heron-like bird, 13c., botor, from Old French butor "bittern," 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.
