Source : Webster's Revised Unabridged Dictionary (1913)

Unexpected \Un`ex*pect"ed\, a.
   Not expected; coming without warning; sudden. --
   {Un`ex*pect"ed*ly}, adv. -- {Un`ex*pect"ed*ness}, n.

Source : WordNet®

unexpectedness
     n : extraordinariness by virtue of being unexpected; "the
         unexpectedness of the warm welcome" [syn: {surprisingness}]
         [ant: {expectedness}]