large person vs somebody

large person and somebody both are nouns.

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

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

large person: a person of greater than average size
somebody: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

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

large person (noun)	somebody (noun)
a person of greater than average size	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential