Late 15th century. From Middle French morne from Old French, Middle French morné blunted, probably from an unattested Old French verb *morner (compare amorner (reflexive) to mortify oneself, amorné sad, amornir (reflexive) to become doleful, amorni sad), probably ultimately from the Germanic base of mourn.

Late 19th century; earliest use found in The Catholic World. From French morne from French Creole (originally Antilles) morne, further etymology uncertain: perhaps alteration of Spanish morro hillock.

Mid 19th century; earliest use found in Alexander Kinglake (1809–1891), historian and travel writer. From French morne.