William Look up William at Dictionary.com
masc. proper name, from Old North French Willaume, Norman form of French Guillaume, of Germanic origin (cognates: Old High German Willahelm, German Wilhelm), from willio "will" (see will (n.)) + helma "helmet," from Proto-Germanic *helmaz "protective covering" (from PIE root *kel- (2) "to cover, conceal, save;" compare helm (n.2)). After the Conquest, the most popular given name in England until supplanted by John.