colloquialism vs fishy

colloquialism is a noun but fishy is not a noun.

Word	Noun	Adjective	Verb	Adverb
colloquialism	Yes	No	No	No
fishy	No	Yes	No	No

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

colloquialism (adjective)	fishy (adjective)
	of or relating to or resembling fish
	not as expected