gentleman's gentleman vs gentleman

gentleman's gentleman and gentleman both are nouns.

Word	Noun	Adjective	Verb	Adverb
gentleman's gentleman	Yes	No	No	No
gentleman	Yes	No	No	No

As nouns, gentleman's gentleman and gentleman are synonyms defined as:

gentleman's gentleman and gentleman: a manservant who acts as a personal attendant to his employer

Other synonyms of gentleman's gentleman include man, valet, valet de chambre.

gentleman's gentleman (noun)	gentleman (noun)
a manservant who acts as a personal attendant to his employer	a man of refinement
	a manservant who acts as a personal attendant to his employer