INCROYABLE

In`croy`a"ble, n. [F., lit., incredible.]

Definition: A French fop or dandy of the time of the Directory; hence, any fop.

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.).

Source: Webster’s Unabridged Dictionary 1913 Edition