DEFINITION:

Panache is a word of French origin that carries the connotation of a flamboyant manner and reckless courage.
The literal translation is a plume, such as is worn on a hat or a helmet, but the reference is to King Henry IV of France. Pleasure-loving and cynical, but a brave military leader and the best-loved of the kings of France, he was famed for wearing a striking white plume in his helmet and for his war cry: "Ralliez-vous à mon panache blanc!" (Follow my white plume!)

CURRENT USE:
Panache is now used to describe someone who has a dashing confidence of style or shows a certain flamboyance and courage and is also a familiar word now in English.  It’s meaning has also been extended to include anything capable of displaying such attributes.