scruff vs back end

scruff and back end both are nouns.

Word	Noun	Adjective	Verb	Adverb
scruff	Yes	No	No	No
back end	Yes	No	No	No

As nouns, back end is a hypernym of scruff; that is, back end is a word with a broader meaning than scruff:

Other hypernyms of scruff include backside, rear.

scruff (noun)	back end (noun)
the back side of the neck	the side of an object that is opposite its front