The Collaborative International Dictionary of English v.0.48:

Wittiness \Wit"ti*ness\, n.
   The quality of being witty.
   [1913 Webster]

WordNet (r) 3.0 (2006):

wittiness
    n 1: a message whose ingenuity or verbal skill or incongruity
         has the power to evoke laughter [syn: wit, humor,
         humour, witticism, wittiness]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "wittiness":
   brilliance, cleverness, comedy, comicality, comicalness, drollery,
   drollness, facetiousness, funniness, humorousness, jocoseness,
   jocularity, joking, joshing, keen-wittedness, keenness,
   nimble-wittedness, pleasantry, pungency, quick-wittedness,
   saltiness, sharpness, smartness