From Greek 'melas' (black) + 'khole' (bile) — depression blamed on excess black bile in the ancient humoral system.
From Greek melankholía (μελαγχολία), a compound of mélas (black, dark) and kholḗ (bile, gall). Rooted in PIE *mel- (dark, dirty) for the first element, and PIE *ghel- (to shine, yellow-green) for the second — ironic, since bile is both yellow and black depending on type. In Hippocratic medicine the body held four humors: blood, phlegm, yellow bile, and black bile. An excess of black bile caused depression, despondency, and irrational fear
'Melancholy,' 'melanin,' 'cholesterol,' and 'cholera' are all body-fluid words. Melancholy is 'black bile.' Melanin is 'the black pigment.' Cholesterol is 'solid bile.' Cholera was named for the vomiting of bile. Two Greek roots — black and bile — permeate English medical and emotional vocabulary.