gentlemanliness vs good manners

gentlemanliness and good manners both are nouns.

Word	Noun	Adjective	Verb	Adverb
gentlemanliness	Yes	No	No	No
good manners	Yes	No	No	No

As nouns, good manners is a hypernym of gentlemanliness; that is, good manners is a word with a broader meaning than gentlemanliness:

gentlemanliness: Gentlemanly behaviour, characteristics of or pertaining to being a gentleman.
good manners: a courteous manner

Other hypernyms of gentlemanliness include courtesy.

gentlemanliness (noun)	good manners (noun)
Gentlemanly behaviour, characteristics of or pertaining to being a gentleman.	a courteous manner