sinew vs brawniness

sinew and brawniness both are nouns.

Word	Noun	Adjective	Verb	Adverb
sinew	Yes	No	No	No
brawniness	Yes	No	No	No

As nouns, sinew and brawniness are synonyms defined as:

Other synonyms of sinew include brawn, heftiness, muscle, muscularity.

sinew (noun)	brawniness (noun)
possessing muscular strength	possessing muscular strength
a cord or band of inelastic tissue connecting a muscle with its bony attachment