man jack vs somebody

man jack and somebody both are nouns.

Word	Noun	Adjective	Verb	Adverb
man jack	Yes	No	No	No
somebody	Yes	No	No	No

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

man jack: a single individual
somebody: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

Other hypernyms of man jack include individual, mortal, person, someone, soul.

man jack (noun)	somebody (noun)
a single individual	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential