Why is the heir to the French throne known as the dauphin which transates to dolphin?

Question

It's been bugging me ever since I found out that dauphin means dolphin. Can anyone enlighten me?

Answer 1

Dauphin
From Wikipedia, the free encyclopedia

The Dauphin was the heir apparent to the throne of France under the Valois and Bourbon dynasties.

Guy VIII, Count of Vienne, had a dolphin on his coat of arms and had been nicknamed le Dauphin (French for dolphin). The title of Dauphin de Viennois descended in his family until 1349, when Humbert II sold his signeurie, called the Dauphiné, to King Philippe VI on condition that the heir of France assumed the title of le Dauphin. The wife of the Dauphin was known as la Dauphine.

The first French prince called le Dauphin was Charles V. The title is roughly equivalent to the English title Prince of Wales.