gentleman's gentleman vs valet de chambre

gentleman's gentleman and valet de chambre both are nouns.

Word	Noun	Adjective	Verb	Adverb
gentleman's gentleman	Yes	No	No	No
valet de chambre	Yes	No	No	No

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

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

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

gentleman's gentleman (noun)	valet de chambre (noun)
a manservant who acts as a personal attendant to his employer	a manservant who acts as a personal attendant to his employer