"state of being answerable," 1770, from accountable + -ity. Earlier was accountableness (1660s).
Entries linking to accountability
accountable adj.
"answerable," literally "liable to be called to account," c. 1400 (mid-14c. in Anglo-French), from Old French acontable; see account (v.) + -able. Related: Accountably.
-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]