The English surname Keynes is derived from a Norman place name, either Cahagnes (Calvados) or Cahaignes (Eure), which are documented as places of origin of people of this name[2] or possibly also from similar placenames not so documented.
The earliest documented person in England bearing the name was William de Cahaignes from Normandy who was born around 1035.
[3] Major tenant of Robert, Count of Mortain (half-brother of William the Conqueror) in several Domesday counties.
His widow Adelicia made a grant for his soul to Lewes priory, with the assent of their son Hugh (Mon.
[4] Surname variants include "Koine", "De Keynes", "Keynes", "de Cayenes", "Caynes", "Caines", "Cheyney", "Cheney", "Chaney", "Chaineis", "Cahaignes", "Casneto", "Caisned", "Casineto".