'le Diable' is unlikely to be a Given name as we would recogise it, since 'second' names tended to be more of a description, ie Fletcher, Butcher, or Johnson etc etc. 'Le Diable' means Devil so is more likely to refer back to some particularly nasty deed foisted on the people of Normandy, in the same way as Anglo Saxon kings were known by a description, such as Edward the Confessor. However, if you're really after a second name for W the C then this might be your best bet.