Dauphin, a name originally given to the Seigneurs of the province of Dauphiné, in allusion to the dolphin which several members of the family wore as a badge, but in 1349 given to the heir-presumptive to the crown of France, when Humbert II., dauphin of Vienne, ceded Dauphiné to Philippe of Valois, on condition that the eldest son of the king of France should assume the title, a title which was abolished after the Revolution of 1830. The word signifies dolphin in French.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Daun, Leopold, Graf von * Dauphiné