buttocks vs excrement

buttocks and excrement both are nouns.

Word	Noun	Adjective	Verb	Adverb
buttocks	Yes	No	No	No
excrement	Yes	No	No	No

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