thinness vs bonyness

thinness and bonyness both are nouns.

Word	Noun	Adjective	Verb	Adverb
thinness	Yes	No	No	No
bonyness	Yes	No	No	No

As nouns, bonyness is a hyponym of thinness; that is, bonyness is a word with a more specific, narrower meaning than thinness:

thinness (noun)	bonyness (noun)
the property of having little body fat	extreme leanness (usually caused by starvation or disease)
relatively small dimension through an object as opposed to its length or width
a consistency of low viscosity
the property of being very narrow or thin
the property of being scanty or scattered; lacking denseness
The property of lacking substance or strength.