dauphin: [15] The eldest sons of the French king were from 1349–1830 designated by a title which is essentially the same word as English dolphin. It was originally applied to the lords of the Viennois, an area in the southeast of France, whose coat of arms incorporated three dolphins. After the Viennois province of Dauphiné was sold by Charles of Valois to the French crown in 1343, the king gave it to his eldest son, and from then on all eldest sons inherited it along with the title dauphin. => dolphin[dauphin etymology, dauphin origin, 英语词源]