Lorcán Ó Muireadhaigh quotes Omeath forms sean-Phroinnsias Mhac Eachmharcaigh and Aodaidh Mhac Eachmharcaigh in An tUltach 3:3 p 7, 4:10 p 6, 8:3 p 7, 8:9 p 3. On an earlier occasion he writes Aodaidh Mhac Chearcaigh (An tUltach 2:7 p 3), which strongly suggests the pronunciation.

The regular weakening of the prefix of a surname after a forename (Mac > Mhac or 'ac; Ó > a) is most important to appreciate.  However, surnames will be written here without such weakening, where they are being used without a forename.  But the weakening should not be forgotten when using a forename with the surname.  This weakening can cause Mac and Ó to fall together in speech, and in some cases is presumably the reason why names are found with either prefix indiscriminately (Mac/Ó Catháin, ?Mac/Ó Cathmhaoil, Mac/Ó Gránna, Mac/Ó Gormáin, etc.); it is certainly the reason in the case of Mac/Ó Grianna (where Mac is the historically correct form), but in the important cases of Mac/Ó Domhnaill and Mac/Ó Néill, both forms are historically correct — the Mac forms came from Scotland and are not directly related to the Ó forms. However doublets are found even where the forms would not entirely fall together phonetically, as in Mac/Ó Brádaigh, Mac/Ó Broin, Mac/Ó Díomasaigh, Mac/Ó Donghaile, Mac/Ó Donnchadha, Mac/Ó Labhraidh, Mac/Ó Labhradha, Mac/Ó Líonacháin, Mac/Ó Murchaidh, Mac/Ó Muireadhaigh, Mac/Ó Rabhartaigh, Mac/Ó T(h)oirdhealbhaigh; Mac/Óh Aodha, Mac/Óh Eochadha, Mac/Óh Eochaidh, Mac/Óh Uiginn.

One other general property of Ulster surnames may be mentioned.  It is not the traditional practice in Ulster to use Mhic and Uí in forming the surnames of married females.  As in Gaelic Scotland, Nic and Ní are used. In other words, "Mary Ward" is "Máire Nic a' Bháird", whether she is Miss or Mrs. For evidence we can point to the dedication to married couples of the church windows in Gort a' Choirce — these are listed in Seán Ó Gallchóir (eag.), Teach Pobail Chríost Rí, Gort a' Choirce 1953–2003, 2003, pp 140–4; a typical example is "Seosamh agus Brighid Nic Giolla Chearr". Or to several Gaelic gravestones in Mevagh cemetery which are misinterpreted if "Ní Dhochartaigh" or "Nic Giolla Bhríde" are taken to be maiden surnames. There are similar examples in Annagry cemetery, eg. the very first stone in that listing has "Máire Nic Pháidín" who was née Bell. There are examples too in the schools folklore collection from Rann na Fearsaide, as found in Rann na Feirsde, Seanchas ár Sinsear by Conall Ó Grianna (1998), eg. "Róise Ní Ghallchobhair" (p 26) was née Ní Dhomhnaill; "Máire Ní Ghrianna" (p 357) was also née Ní Dhomhnaill. Or again, take a typical 1911 census form from the townland of Mín na Leice, where the married daughter of the Mac Giolla Easpaig family is named as "Nuala Ní Dhubhgain". Anyone desirous of further evidence can check the female surnames in Tobar na Gaedhilge and whether their fictitious bearers were single or married! (To indicate the marital status explicitly, Mrs (Mary) Ward is "(Máire) Bean Mhic a' Bháird" and Miss (Mary) Ward is "(Máire) Nighean Mhic a' Bháird".

We sometimes find that a Gaelic surname is reduced or shortened, eg. Mac an Déanaigh to Mac an Éanaigh, or Mac Giolla Fhinnéin to Mac Shlinnéin.   Such shortened forms may be the basis for bizarre mis-translations (respectively: Bird and Shoulder).  Some of the names presented in the first column here may yet turn out to be reduced forms of names still to be added.

Other sources drawn on include the following:
Livingstone, Peadar: "Roinnt de shloinnte Fhearnmhaí", An tUltach 60:4 (4/1983) 14–16 (leagan Gaedhilge le P Ó Casaide)

One of the interesting things about anglicizations of Gaelic names, whether personal names or place-names, is that they are often a more reliable guide to the former local Gaelic pronounciation than Irish forms introduced in the course of the language revival and given a non-local pronunciation. If the anglicised forms of surnames can be located to specific areas, they may — in conjunction with place-names, and with the variable pronunciation of personal names — provide evidence for the nature of geographical variation in the erstwhile spoken Gaelic of East Ulster.

Tá rud le rádh ag Seán Mac Maoláin fá na sloinnte i dTír Chonaill i measc a bhfuil aige annseo.

If you use this page to locate the Gaelic sources of a particular anglicization, remember that not all possible Gaelic names are included here — far from it.

This page may also contain assorted notes on Ulster Gaelic surnames.

General and specific reading

MacLysaght, Edward: The surnames of Ireland (1957)
Bell, Robert: The book of Ulster surnames (1988)
Turner, Brian: various works
Dillon, Charlie: Sloinnte / surnames
Smyth, William J: Atlas of Irish Names

Confusion between Ó and Mac

There are circumstances where Ó and Mac can sound the same, and where there may be uncertainty over which one to write, knowing only the pronunciation of a surname.

In Ulster, it is normal for the m of Mac to be lenited or even silent in a surname — it is often written as Mhac or 'ac.  Now, if the next part of the surname begins with C or G, this merges with the c of 'ac, and it is impossible to know from the sound whether the surname contains Mac or Ó.  The vowel in either particle will be an obscure one, and the following k sound could come from Mac or from the next part of the name.  This has often been noted, e.g. McLysaght (More Irish Families, p. 117) remarks on the "not uncommon substitution of Ó for Mac with names beginning with C, G and K".  Such substitutions were not confined to the ignorant — one was made by a leading southern Gaelic scholar when he wrote Ó Coilín for a Donegal 'ac Ailín (Royal Irish Academy Minutes of Proceedings, Session 1931–32, p. 30)!  Seán Ó hEochaidh confirmed to me that the family in question here — some of whom later settled in Killybegs — employed the anglicisation "Campbell", as is usual for 'ac Ailín.  They are named "Campbell" in the 1901 and 1911 census returns for Mín a' Droighin.

Ó Droighneáin (An Sloinnteoir Gaeilge agus an tAinmneoir,  1972, p. vii) raises the case of the writers from Rann na Fearsaide, the brothers Séamus Ó Grianna and Seosamh Mac Grianna.  Their surname is pronounced ə'griəɴə — but should it be written Ó Grianna or 'ac Grianna? The sound cannot tell us which. As schooling and other official matters would have used the anglicised form Greene, the question would not have arisen until the brothers began to write in Irish and the name had to be printed in its original Irish form.  The elder brothers, Séamus (1889–1969) and Domhnall (1894–1962), chose the more direct Ó Grianna. Some historical research, however, disclosed that the correct historical form of the name was Mac Grianna (actually, Mac Grianra), and this form was adopted by the younger brothers, Seosamh (1900–1990) and Seán Bán (1905–1979), and also — possibly earliest — by their cousin Domhnall Frank (c1894–1972).

This explanation of the fact that two brothers are known as Séamus Ó Grianna and Seosamh Mac Grianna is very fully given by Gearóid Stockman in his book Cruinneas Gramadaí agus Corrfhocal Eile (1996) on pp. 99–100.  Hopefully it has laid to rest the ludicrous suggestion that the divergence of surname may have been "agreed on ... either to avoid confusion of them as writers, or for simple difference of taste when they adopted the Irish forms of the English name Green [sic]" (Brady and Cleeve, A Biographical Dictionary of Irish Writers, 1985, p. 311; partially repeated in McRedmond, Modern Irish Lives, 1996). The problem was not to "invent an Irish form" for Greene; it was to find a way to write the oral ə'griəɴə.

Regarding the second element of the name, like Professor Stockman, I too heard the late Seán Bán Mac Grianna trace the family's origins to Termon near Kilmacrenan. He had arrived at the conclusion that the proper written form is Mac Grianra. Support comes from the fact that McGrenry is a name associated with the Termon area, whence it has spread to Derry and Belfast. But Greene is the preferred anglicisation in north-western Donegal, and McLysaght (More Irish Families, p. 219) notes written Irish forms from Donegal in 1602 which lack the second r. Much of this information is also given by Uinseann Ó Dónaill (Vincie Shíle) in the Donegal Annual (1987) p. 59.