[bit.tern] n [ME bitoure, fr. MF butor, fr. (assumed) VL butitaurus, fr. L buteo hawk + taurus bull] (1515): any of various small or medium-sized usu. secretive herons (esp. genera Botaurus and Ixobrychus)
[2]bittern n [irreg. fr. [1]bitter] (1682): the bitter water solution of salts that remains after sodium chloride has crystallized out of a brine