boy Friday vs adult male

boy Friday and adult male both are nouns.

Word	Noun	Adjective	Verb	Adverb
boy Friday	Yes	No	No	No
adult male	Yes	No	No	No

As nouns, adult male is a hypernym of boy Friday; that is, adult male is a word with a broader meaning than boy Friday:

Other hypernyms of boy Friday include assistant, help, helper, supporter, man.

boy Friday (noun)	adult male (noun)
a male assistant who has a range of duties	an adult person who is male (as opposed to a woman)