Cnut was king of England from 1016-1035. A famous story depicts him trying to command the tides of the Thames River, unsuccessfully. The name is also spelled Canute.
Cnut was the name of some Scandinavian guy we studied in history. Whenever I hear this name I burst into hysterics. If I met someone named Cnut I would immediately assume that they were crazy. Then I would ask them if they could crack nuts without a nutcracker.