Dauphin

Dauphin, a title originally borne by the eldest sons of the princes of Vienne and of other great feudal lords. When Dauphine and Vienne were ceded to the French crown in 1343, Humbert II., their king, made it a condition of the cession that the title should be borne by the eldest son of the French king, and it was so borne down to the Revolution. The name, according to Littre, is a proper name - the same as delphinus, Fr. dauphin, a dolphin. The seigneurs of Dauphine bore three dolphins as arms. Other and more fanciful explanations have been given - one that the word is merely a corruption of "de Vienne," assimilated by popular etymology to the spelling of the name of the fish; another that it arose from the fact that a dolphin was the crest of one of the Counts of Vienne.