There are no exact historical accounts as to why but according to popular ones it is said that one of the earliest Princes of Wales, Edward "The Black Prince", obtained the motto from the badge of John I of Bohemia following the battle of Crécy. read more
The Prince of Wales's feathers is the heraldic badge of the Prince of Wales. It consists of three white ostrich feathers emerging from a gold coronet. A ribbon below the coronet bears the motto Ich dien (, German for "I serve"). read more
So with the feathers and the dead King’s motto etc, made his own new badge which today is the Prince of Wales badge. “Eych Dyn” in Welsh means “Your Man”. “Ich Dien” in German means “I Serve”. So as both the German and Welsh words are pronounced the same, it is thought he used this motto to honour Welsh soldiers. read more