The story
Circa 1600, from mump (“grimace”, noun), compare mump (verb), most likely referring to the painful difficulty in swallowing.
Etymology from Wiktionary, CC BY-SA 4.0.
mumps
Today it means: A contagious disease caused by the Mumps virus of the genus Rubulavirus, mostly occurring in childhood, which causes swelling of glands in the face and neck. Full definition →