paddy wagon vs black Maria

paddy wagon and black Maria both are nouns.

Word	Noun	Adjective	Verb	Adverb
paddy wagon	Yes	No	No	No
black Maria	Yes	No	No	No

As nouns, paddy wagon and black Maria are synonyms defined as:

Other synonyms of paddy wagon include patrol wagon, police van, police wagon, wagon.

paddy wagon (noun)	black Maria (noun)
van used by police to transport prisoners	van used by police to transport prisoners