(male) Probably the most successful of all the Old French names of Germanic origin that were introduced to England by the Normans. It is derived from Germanic wil ‘will, desire’ + helm ‘helmet, protection’. The fact that it was borne by the Conqueror himself does not seem to have inhibited its favour with the ‘conquered’ population: in the first century after the Conquest it was the commonest male name of all, and not only among the Normans. In the later Middle Ages it was overtaken by John, but continued to run second to that name until the 20th century, when the picture became more fragmented.
Short forms: Will, Bill.
Pet forms: Willy, Willie, Billy.
Cognates: Irish: Uilliam. Scottish Gaelic: Uilleam. Welsh: Gwilym. German: Wilhelm. Dutch: Willem. Scandinavian: Vilhelm. French: Guillaume. Spanish: Guilermo. Catalan: Guillem. Portuguese: Guilherme. Italian: Guglielmo. Czech: Vilém. Slovenian: Viljem. Hungarian: Vilmos. Lithuanian: Vilhelmas. Latvian: Vilhelms.
Irish: reduced form of O’Hayden, an Anglicized form of Gaelic Ó hÉideáin and Ó hÉidín ‘descendant of Éideán’ or ‘descendant of Éidín’, personal names apparently from a diminutive of éideadh ‘clothes’, ‘armor’. There was also a Norman family bearing the English name (see 2 below), living in County Wexford.
English: habitational name from any of various places called Hayden or Haydon. The three examples of Haydon in Northumberland are named from Old English hēg ‘hay’ + denu ‘valley’. Others, for example in Dorset, Hertfordshire, Somerset, and Wiltshire, get the name from Old English hēg ‘hay’ (or perhaps hege ‘hedge’ or (ge)hæg ‘enclosure’) + dūn ‘hill’.
Jewish: see Heiden.