bit·tern 1 
(b
ĭt
ərn)
n. Any of several wading birds of the genera Botaurus and Ixobrychus, having mottled brownish plumage and, in most species, a deep booming cry in the male.
[Alteration (perhaps influenced by TERN1) of Middle English bitour, from Old French butor, possibly from Vulgar Latin *buti-taurus : Latin būtiō, buzzard + Latin taurus, bull (after its cry); see tauro- in the Appendix of Indo-European roots.]