This wouldn't have happened if William the Conqueror was known as William the Conquered.
For those who are curious, the loser in the Battle of Hastings was Harold II of England (or Harold Godwinson as his father was Godwin, Earl of Wessex).
Interestingly enough, we do remember King Cnut, whose sister married Harold II's uncle.
https://en.wikipedia.org/wiki/William_the_Conqueror#cite_not...