back end vs nape

back end and nape both are nouns.

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

As nouns, nape is a hyponym of back end; that is, nape is a word with a more specific, narrower meaning than back end:

Other hyponyms of back end include nucha, scruff, rearward.

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