These names, with occasional variants like MacElvey, are the modern anglicized forms of Mac Giolla Bhuidhe. The Four Masters under date 1181 mention two leading men of Connacht called Mac Giolla Buidhe (translated by O'Donovan as MacGillaboy). In 1392 Richard MacIlboy was a citizen of Limerick.

These are dealt with under Gilbey (q.v. supra). Earlier anglicizations such as MacGilleboy were fairly close to the original: one of these, MacIleboy, appears as a principal Irish name in the barony of Upper Iveagh, Co. Down, in the “census” of 1659. In the same document we find Gilbert MacIlwee, a titulado in Letterkenny town. That is in Co. Donegal which, with the adjacent parts of Co. Tyrone, is the principal location of MacKelvey, MacElwee etc. today. In the Tribes & Customs of Hy Fiachrach and in O'Donovan's notes thereto Mac Giolla Bhuidhe is placed in the barony of Carra (Co. Mayo) under the O'Gormleys: O'Donovan says that there the name was anglicized Kilboy. This form of the name is still extant in north Connacht, where it is presumably a distinct sept, not a branch of that located in Ulster.

Other synonyms of MacKelvey reported by local registrars in 1890 were MacCalvey, MacCelvey, MacElvee, MacElvie, MacGilvie, MacKilvie and Kilvey. A few years earlier MacElvea and MacElvoy were recorded. Woulfe gives several other rare variants. It will be observed that MacKelvey is a name with which the prefix Mac has been consistently retained, though the simple Kelvey is occasionally found. The late Mr. J. C. MacDonagh in a map showing the present location of Donegal surnames, which he kindly prepared for me, places MacElwee in Inishowen and MacGilway further south. Here we must take note of the fact that the name Calvey is almost peculiar to Counties Mayo and Sligo.

Woulfe gives Mac an Chalbhaigh as the Gaelic-Irishform of Calvey, and of MacCalvey, with no indication of the part of the country to which they belong. MacCalvey does not appear in the birth registrations 1864-66.