-
A common termination of nouns of Latin origin or formed after Latin analogy, from adjectives, properly from adjectives of Latin origin or type, as in activity, civility, suavity, etc., but also in some words from adjectives not of Latin origin or type, as in jollity. The suffix is properly -ty, the preceding vowel belonging originally to the adjective. See -ty.
(noun)
The Century Dictionary (Public Domain)