small person vs somebody

small person and somebody both are nouns.

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

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

small person: a person of below average size
somebody: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

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

small person (noun)	somebody (noun)
a person of below average size	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential