japery vs clowning

japery and clowning both are nouns.

Word	Noun	Adjective	Verb	Adverb
japery	Yes	No	No	No
clowning	Yes	No	No	No

As nouns, japery and clowning are synonyms defined as:

Other synonyms of japery include buffoonery, frivolity, harlequinade, prank.

japery (noun)	clowning (noun)
acting like a clown or buffoon	acting like a clown or buffoon
	a comic incident or series of incidents