versatility (n.)

c. 1600, "inconstant," from Latin versatilis "turning, revolving, moving, capable of turning with ease to varied subjects or tasks," from past participle stem of versare "keep turning, be engaged in something, turn over in the mind," frequentative of vertere "to turn" (from PIE root *wer- (2) "to turn, bend"). Meaning "able to do many things well" is from 1762 in English.

word-forming element making abstract nouns from adjectives and meaning "condition or quality of being ______," from Middle English -ite, from Old French -ete (Modern French -ité) and directly from Latin -itatem (nominative -itas), suffix denoting state or condition, composed of -i- (from the stem or else a connective) + the common abstract suffix -tas (see -ty (2)).

Roughly, the word in -ity usually means the quality of being what the adjective describes, or concretely an instance of the quality, or collectively all the instances; & the word in -ism means the disposition, or collectively all those who feel it. [Fowler]