"quality of being justifiable; possibility of being defended or excused," 1835, from justifiable + -ity. Justifiableness is from 1630s.
Entries linking to justifiability
justifiable adj.
"capable of being proved just or true, morally defensible," 1520s, from Old French justifiable, from justifiier (see justify). Earlier in same sense was justificable (mid-15c.). Related: Justifiably (mid-15c.).
-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]