The Collaborative International Dictionary of English v.0.48:

Fickleness \Fic"kle*ness\, n.
   The quality of being fickle; instability; inconsonancy.
   --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fickleness
    n 1: unfaithfulness by virtue of being unreliable or treacherous
         [syn: faithlessness, falseness, fickleness,
         inconstancy]

The Devil's Dictionary (1881-1906):

FICKLENESS, n.  The iterated satiety of an enterprising affection.