mid-15c., "that is to be kept without violation" (of an oath, etc.), from Latin inviolabilis "inviolable, invulnerable," from in- "not, opposite of" (see in- (1)) + violabilis "that may be injured, easily wounded," from violare "to do violence to" (see violation). Meaning "having a right or guaranty of immunity" (of a place of sanctuary, etc.) is from 1570s. Meaning "incapable of being injured" is from 1520s. Related: Inviolably.
-ity
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]