Scottish and Irish patronymic surnames frequently have the prefix Mac or Mc.
When these surnames were originally developed, they were formed by adding the Gaelic word mac, which means son of, to the name of the original bearer's father. For example, the surname MacDougall literally means son of Dougal.
In later times, these prefixes were also added to the occupation or nickname of the bearer's father. For example, MacWard means son of the bard and MacDowell means son of the black stranger.
Numerous variations of this prefix emerged, for a number of reasons. It was rendered Mag before vowels and aspirated consonants.
Historical records concerning Irish and Scottish names reveal that the common prefix Mc and the less common prefixes M' and Mcc developed as abbreviations of the original Gaelic prefix Mac.
Thus, the popular beliefs that Mc is a distinctively Irish prefix while Mac is exclusively Scottish, and that one prefix is used by Catholic families while the other one is specifically Protestant are erroneous.
In actuality, the same person often had their surname recorded using both Mac and Mc on separate occasions.
In hopes of finally clearing this misnomer, we are including a quote from Irish Families written Edward MacLysaght (1887-1986), Chairman of Irish Manuscripts, former Chief Herald of Ireland:
I may refer here to the widespread belief outside Ireland the Mac is essentially a Scottish prefix. To us this idea is absurd. For many of our foremost Irish families bear Mac names such as MacCarthy, MacDermot, MacGuinness, MacGrath, MacGillycuddy, MacKenna, MacMahon, MacNamara and so on. Nevertheless, it is a fallacy widely held.[1]
To further emphasize the point, we draw your attention to another Chief Herald of Ireland, John O'Hart (1824-1902) author of countless books Irish genealogies including Irish Pedigrees in which he notes the following under the title Irish Adfixes
Mac, the son or descendant of; as Cormac MacAirt, "Cormas the son of Art; MacDonnell, "the descendants of Donall," etc[2]