The Collaborative International Dictionary of English v.0.48:

Ton \Ton\ (t[^o]n), n. [F. See Tone.]
   The prevailing fashion or mode; vogue; as, things of ton.
   --Byron.
   [1913 Webster]

         If our people of ton are selfish, at any rate they show
         they are selfish.                        --Thackeray.
   [1913 Webster]

   Bon ton. See in the Vocabulary.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bon ton \Bon" ton"\ (b[^o]N" t[^o]N"). [F., good tone, manner.]
   The height of the fashion; fashionable society.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bon ton
    n 1: the fashionable elite [syn: society, high society,
         beau monde, smart set, bon ton]