excrement vs rear end

excrement and rear end both are nouns.

Word	Noun	Adjective	Verb	Adverb
excrement	Yes	No	No	No
rear end	Yes	No	No	No

excrement (noun)	rear end (noun)
waste matter (as urine or sweat but especially feces) discharged from the body	the fleshy part of the human body that you sit on