1580s, "function or manners of a stage clown or jester," from clown (n.) + -age. From 1630s as "actions or behavior of a rustic."
Entries linking to clownage
clown n.
1560s, clowne, also cloyne, "man of rustic or coarse manners, boor, peasant," a word of obscure origin; the original form and pronunciation are uncertain. Perhaps it is from Scandinavian dialect (compare Icelandic klunni "clumsy, boorish fellow;" Swedish kluns "a hard knob; a clumsy fellow," Danish klunt "log, block"), or from Low German (compare North Frisian klönne "clumsy person," Dutch kloen). OED describes it as "a word meaning originally 'clod, clot, lump', which like those words themselves ..., has been applied in various langs. to a clumsy boor, a lout."
The theory that it is from Latin colonus "colonist, farmer" is less likely, but awareness of the Latin 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[alian] comedy" [Weekley]. Meaning "contemptible person" is from 1920s. Fem. form clowness attested from 1801.
-age
word-forming element in nouns of act, process, function, condition, from Old French and French -age, from Late Latin -aticum "belonging to, related to," originally neuter adjectival suffix, from PIE *-at- (source of Latin -atus, past participle suffix of verbs of the first conjugation) + *-(i)ko-, secondary suffix forming adjectives (see -ic).