If I am not mistaken, modern English language has a large influence from Old French through the Norman invasion by William the Conqueror in 1066 and subsequent Norman monarchs.
But if the new rulers brought with them their language, why aren't monarchs today called something derived from roi and reine, or something along those lines?
Is it something the new rulers chose, maybe to bring themselves closer to their new subjects? Or did the population keep calling the new rulers cyning and cwen, regardless of the language the rulers brought with them, and it simply stuck? Or is it something completely different?