specificity (n.)

1630s, "having a special quality," from French spécifique and directly from Late Latin specificus "constituting a kind or sort" (in Medieval Latin "specific, particular"), from Latin species "kind, sort" (see species) +  -ficus "making, doing," from combining form of facere "to make." Earlier form was specifical (early 15c.). Meaning "definite, precise" first recorded 1740. Related: Specifically; specificness.

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]