backside vs scruff

backside and scruff both are nouns.

Word	Noun	Adjective	Verb	Adverb
backside	Yes	No	No	No
scruff	Yes	No	No	No

As nouns, scruff is a hyponym of backside; that is, scruff is a word with a more specific, narrower meaning than backside:

Other hyponyms of backside include nape, nucha, rearward.

backside (noun)	scruff (noun)
the fleshy part of the human body that you sit on	the back side of the neck
the side of an object that is opposite its front