Wordorigins.org

Prince Edward Island is named for the fourth son of George III in 1798. The prince, who was also the Duke of Kent, commanded troops in Halifax at the time and had improved the fortifications of Charlottetown on the island. Edward was also the father of Queen Victoria, although she wasn’t born until 1819 and this fact had no bearing on the naming of the island.

Prior to this, the island had been named St. John’s Island, the name of which had been inherited from the French Île Saint-Jean.

(Sources: Dictionary of Canadian Place Names; Illustrated Dictionary of Place Names)