William Kelly

(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.

Irish: Anglicized form of Gaelic Ó Ceallaigh ‘descendant of Ceallach’, an ancient Irish personal name, originally a byname meaning ‘bright-headed’, later understood as ‘frequenting churches’ (Irish ceall). There are several early Irish saints who bore this name. Kelly is now the most common of all Irish family names in Ireland.