/ ˌmelənˈkəʊliə; NAmE -ˈkoʊ-/ noun
( old-fashioned ) a mental illness in which the patient is depressed and worried by unnecessary fears
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WORD ORIGIN
late Middle English (denoting black bile): from late Latin from Greek melankholia , from melas , melan- black + kholē bile, an excess of which was formerly believed to cause depression.