Comedones, a name applied to the little cylinders of sebaceous and epithelial substance which are apt to accumulate in the follicles of the skin and to appear on the surface as small round black spots. When squeezed out they have the appearance of minute maggots or grubs, with black heads, and thence have derived their name.


Entry from Everybody's Cyclopedia, 1912.

(Strictly speaking, the Latin singular of "comedones" is "comedo," but English speakers use both "comedone" and "comedo" as the singular.)