incroyable

from The Collaborative International Dictionary of English v.0.48

Incroyable \In`croy`a"ble\, n. [F., lit., incredible.]
   A French fop or dandy of the time of the Directory; hence,
   any fop.

   Note: The name is said to have been given in allusion not
         only to the extravagant dress, but also to the frequent
         use of the phrase "C'est vraiment incroyable" (That is
         really incredible.).
         [Webster 1913 Suppl.]