melancholy [ME] According to the medieval theory of the four humours (see humour), melancholy or black bile caused depression. The word goes back to Greek melankholia, from melas ‘black’ (source of mid 19th-century melanin and melanoma) and kholē ‘bile’ (source of cholera [LME], choleric [ME], and cholesterol [L19th]). Today it tends to refer to a pensive or moody sadness rather than deep depression.