mettle vs braveness

mettle and braveness both are nouns.

Word	Noun	Adjective	Verb	Adverb
mettle	Yes	No	No	No
braveness	Yes	No	No	No

As nouns, braveness is a hypernym of mettle; that is, braveness is a word with a broader meaning than mettle:

mettle: the courage to carry on
braveness: a quality of spirit that enables you to face danger or pain without showing fear

Other hypernyms of mettle include bravery, courage, courageousness.

mettle (noun)	braveness (noun)
the courage to carry on	a quality of spirit that enables you to face danger or pain without showing fear