dead person vs somebody

dead person and somebody both are nouns.

Word	Noun	Adjective	Verb	Adverb
dead person	Yes	No	No	No
somebody	Yes	No	No	No

As nouns, somebody is a hypernym of dead person; that is, somebody is a word with a broader meaning than dead person:

dead person: someone who is no longer alive
somebody: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

Other hypernyms of dead person include individual, mortal, person, someone, soul.

dead person (noun)	somebody (noun)
someone who is no longer alive	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential