the great unwashed vs hoi polloi

the great unwashed and hoi polloi both are nouns.

Word	Noun	Adjective	Verb	Adverb
the great unwashed	Yes	No	No	No
hoi polloi	Yes	No	No	No

As nouns, the great unwashed and hoi polloi are synonyms defined as:

Other synonyms of the great unwashed include mass, masses, multitude, people.

the great unwashed (noun)	hoi polloi (noun)
the common people generally	the common people generally