(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: from a pet form of David.
English: from the Middle English personal name Day(e) or Dey(e), Old English Dæi, apparently from Old English dæg ‘day’, perhaps a short form of Old English personal names such as Dægberht and Dægmund. Reaney, however, points to the Middle English word day(e), dey(e) ‘dairy maid’, ‘(female) servant’ (from Old English dæge, cognate with Old Norse deigja ‘female servant’, ultimately from a root meaning ‘to knead’, and related to the word for dough), which he says came to be used for a servant of either sex.
Irish: Anglicized form of Gaelic Ó Deaghaidh (see O’Dea).
Scottish: from an Anglicized form of the Gaelic personal name Daìdh, a colloquial form of David.
Welsh: from Dai, a pet form of the personal name Dafydd, Welsh form of David.
FOREBEARS This name was brought independently from many parts of Britain to New England by many bearers from the 17th century onward. Robert Day was one of the founders of Hartford, CT, (coming from Cambridge, MA, with Thomas Hooker) in 1635.