banana peel vs banana skin

banana peel and banana skin both are nouns.

Word	Noun	Adjective	Verb	Adverb
banana peel	Yes	No	No	No
banana skin	Yes	No	No	No

As nouns, banana peel and banana skin are synonyms defined as:

banana peel and banana skin: the skin of a banana (especially when it is stripped off and discarded)

banana peel (noun)	banana skin (noun)
the skin of a banana (especially when it is stripped off and discarded)	the skin of a banana (especially when it is stripped off and discarded)