Duke of Normandy as the reign of William II (1035–87), the ruler of Normandy could style himself "prince and duke, count of Normandy" as if unsure what his title should be. The literal Latin equivalent of "Duke of Normandy", "dux Normanniae", was in use by 1066, but it did not supplant "dux Normannorum" until the Angevin period (1144–1204), at a time when Norman identity was fading. Richard I experimented with the title "marquis" ("marchio") as early as 966, when it was also used in a diploma of King Lothair. Richard II occasionally used it, but he seems to have preferred the title duke.
Frederick William, Duke of Cieszyn Frederick William, Duke of Cieszyn Frederick William of Cieszyn (, , ; 9 November 1601 – 19 August 1625) was a Duke of Cieszyn since 1617 until his death. He was the third but only surviving son of Adam Wenceslaus, Duke of Cieszyn, by his wife Elisabeth, daughter of Gotthard Kettler, Duke of Courland. His mother died from childbirth complications ten days after his birth, on 19 November 1602. Since his early years, Frederick William's education was entrusted to the Silesian humanist Baltzar Exner. In 1611 Duke Adam Wenceslaus decided to convert to the Catholicism, and all the Protestant members