Archaic term for black bile, one of the four bodily humors in ancient and medieval medicine, supposedly causing melancholy.
From Latin atra bilis literally 'black bile' (atra 'black' + bilis 'bile'). From ancient Greek medical theory adopted by medieval and Renaissance physicians.
The entire concept of 'melancholy' comes from Greek melas 'black' + chol 'bile'—medieval doctors literally believed dark thoughts came from dark colored body fluid!
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