fanny vs tail end

fanny and tail end both are nouns.

Word	Noun	Adjective	Verb	Adverb
fanny	Yes	No	No	No
tail end	Yes	No	No	No

As nouns, fanny and tail end are synonyms defined as:

fanny (noun)	tail end (noun)
the fleshy part of the human body that you sit on	the fleshy part of the human body that you sit on
external female sex organs	any projection that resembles the tail of an animal
	the time of the last part of something