colloquialism vs honest-to-god

colloquialism is a noun but honest-to-god is not a noun.

Word	Noun	Adjective	Verb	Adverb
colloquialism	Yes	No	No	No
honest-to-god	No	Yes	No	No

colloquialism (noun)	honest-to-god (noun)
a colloquial expression; characteristic of spoken or written communication that seeks to imitate informal speech

colloquialism (adjective)	honest-to-god (adjective)
	(used informally especially for emphasis) real or genuine