1540s, "pertaining to bile, biliary," from French bilieux, from Latin biliosus "pertaining to bile," from bilis (see bile). Meaning "wrathful, peevish, ill-tempered" (as people afflicted with an excess of bile were believed to be) is attested from 1560s. This is the main modern sense in English and French; the more literal meaning being taken up by biliary. Related: Biliousness.