(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.
English: of much discussed but uncertain origin. 1. It may be from a medieval personal name, but if so the form is unclear. 2. Alternatively, it may be a nickname for a quarrelsome or deceitful person, from Middle English bar(r)et(t)e, bar(r)at ‘trouble’, ‘strife’, ‘deception’, ‘cheating’ (Old French barat ‘commerce’, ‘dealings’, a derivative of barater ‘to haggle’).
It is possible that the original sense of barat survived unrecorded into Middle English as a word for a market trader; the Italian cognate Baratta has this sense. It could also be a nickname or metonymic occupational name from Old French barette ‘cap’, ‘bonnet’.