clown (n.)
1560s, clowne, also cloyne, "rustic, boor, peasant," origin uncertain. Perhaps from Scandinavian dialect (compare Icelandic klunni "clumsy, boorish fellow;" Swedish kluns "a hard knob; a clumsy fellow," Danish klunt "log, block"), or akin to North Frisian klönne "clumsy person." Or, less likely, from Latin colonus "colonist, farmer," though awareness of this word might have influenced the sense development in English.

Meaning "professional fool, professional or habitual jester" is c.1600. "The pantomime clown represents a blend of the Shakes[pearean] rustic with one of the stock types of the It. comedy" [Weekley]. Meaning "contemptible person" is from 1920s. Fem. form clowness attested from 1801.
clown (v.)
c.1600, "to play the clown onstage," from clown (n.); colloquial sense of "to behave inappropriately" (as in clown around, 1932) attested by 1928, perhaps from theatrical slang sense of "play a (non-comical) part farcically or comically" (1891). Related: Clowned; clowning.