Advances in dentistry have been hard on the verb mump. When the word appeared in the late sixteenth century, it meant to chew with toothless gums, but it appears to have died out in the nineteenth century, about the same time that porcelain dentures began to be marketed on a large scale. Mump could also mean to grimace, a sense that is still apparent in mumps, a disease which inflames the salivary glands, resulting in a grimacing appearance.