dirty dog vs so-and-so

dirty dog and so-and-so both are nouns.

Word	Noun	Adjective	Verb	Adverb
dirty dog	Yes	No	No	No
so-and-so	Yes	No	No	No

As nouns, dirty dog and so-and-so are synonyms defined as:

dirty dog and so-and-so: a person who is deemed to be despicable or contemptible

Other synonyms of dirty dog include bum, crumb, git, lowlife, puke, rat, rotter, scum bag, scumbag, skunk, stinker, stinkpot.

dirty dog (noun)	so-and-so (noun)
a person who is deemed to be despicable or contemptible	a person who is deemed to be despicable or contemptible