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]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "bon ton":
   conformity, consuetude, convention, currency, custom,
   established way, etiquette, fashion, fashionableness, folkway,
   haute couture, high fashion, manner, manners, mode, modishness,
   mores, observance, popularity, practice, praxis, prescription,
   prevailing taste, prevalence, proper thing, ritual,
   social convention, standard behavior, standard usage,
   standing custom, stream of fashion, style, stylishness, swim,
   time-honored practice, tradition, trend, usage, use, vogue,
   voguishness, way, what is done, wont, wonting