tail end vs fundament

tail end and fundament both are nouns.

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

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

tail end and fundament: the fleshy part of the human body that you sit on

tail end (noun)	fundament (noun)
the fleshy part of the human body that you sit on	lowest support of a structure
any projection that resembles the tail of an animal	the fleshy part of the human body that you sit on
the time of the last part of something	the fundamental assumptions from which something is begun or developed or calculated or explained