half-wit vs colloquialism

half-wit and colloquialism both are nouns.

Word	Noun	Adjective	Verb	Adverb
half-wit	Yes	No	No	No
colloquialism	Yes	No	No	No

half-wit (noun)	colloquialism (noun)
a stupid incompetent person	a colloquial expression; characteristic of spoken or written communication that seeks to imitate informal speech
a person of subnormal intelligence