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.
William I, Duke of Bavaria William I, Duke of Bavaria William I, Duke of Bavaria-Straubing (Frankfurt am Main, 12 May 1330 – 15 April 1389, Le Quesnoy), was the second son of the emperor Louis IV the Bavarian from his second wife Margaret of Holland and Hainaut. He was also known as William V, Count of Holland, as William III, Count of Hainaut and as William IV, Count of Zeeland. In 1345 William's father was conferring Hainaut, Holland, Zeeland and Friesland upon his wife Margaret, and shortly later also upon their son William. After his father's death in 1347 William ruled Bavaria, Holland and Hainaut