knave vs rapscallion

knave and rapscallion both are nouns.

Word	Noun	Adjective	Verb	Adverb
knave	Yes	No	No	No
rapscallion	Yes	No	No	No

As nouns, knave and rapscallion are synonyms defined as:

Other synonyms of knave include rascal, rogue, scalawag, scallywag, varlet.

knave (noun)	rapscallion (noun)
one of four face cards in a deck bearing a picture of a young prince	one who is playfully mischievous
a deceitful and unreliable scoundrel	a deceitful and unreliable scoundrel