The Collaborative International Dictionary of English v.0.48:
Becomingness \Be*com"ing*ness\, n. The quality of being becoming, appropriate, or fit; congruity; fitness. [1913 Webster] The becomingness of human nature. --Grew. [1913 Webster]WordNet (r) 3.0 (2006):
becomingness n 1: the quality of being becoming [ant: unbecomingness]