Source : Webster's Revised Unabridged Dictionary (1913)

Becomingness \Be*com"ing*ness\, n.
   The quality of being becoming, appropriate, or fit;
   congruity; fitness.

         The becomingness of human nature.        --Grew.

Source : WordNet®

becomingness
     n : the quality of being becoming [ant: {unbecomingness}]