colloquialism vs month of Sundays

colloquialism and month of Sundays both are nouns.

Word	Noun	Adjective	Verb	Adverb
colloquialism	Yes	No	No	No
month of Sundays	Yes	No	No	No

colloquialism (noun)	month of Sundays (noun)
a colloquial expression; characteristic of spoken or written communication that seeks to imitate informal speech	a time perceived as long