Mac, Gaelic for "son", is the most common element of Scottish and Irish surnames. In both countries, Mc is always an abbreviation of Mac. There is absolutely no truth to the American myth at Mac is Scottish and Mc is Irish. Mac used to be abbreviated M' although this spelling is not common now. At times, all three versions can be seen in an early book on Highland music, the author spelled his own family name three different ways on the first two pages -- "MacDonald", "McDonald", and "M'Donald."
Black's "The Surnames of Scotland" and MacLysaght's "The Surnames of Ireland" both treat Mac in the same way -- as the only and original spelling. Persons seeking a name spelled "Mc" are expected to know that it is a conventional abbreviation forMac. This same approach is used in "Tartan For Me!" To find "McDeal" look for "MacDeal."
Mac is always considered an addition to a name. Before there was a "Donald's Son" there was a "Donald". In both Scotland and Nova Scotia, names beginning with Mac were traditionally alphabetized under the first letter of the second name --MacArthur under "A", MacZeal under "Z". Many Scots dropped "Mac" as they became Anglicized or emigrated, "Mac Wyeth" becoming simply "Wyeth". "Kinzie" is from "MacKenzie". The one notable exception is the Innes and MacInnes families, each quite distinct. The Innes family have Pictish roots and are from the east coast of Scotland with a red tartan. The MacInnes are of Gaelic origin from the west coast and wear a green tartan.
Mac takes a variety of pronunciations. In Islay Gaelic, Mac is pronounced like /mek/. In the United States one hears it as "mick". Preceding a /k/ or /g/ sound, the final /k/ of Mac disappears. It became the practice in both the south of Scotland and in Ireland to write two words as one (MacGill to Magill; MacHale to Makale). In other names the /k/ sound of Mac is duplicated and attached to the front of a following word if it begins in a vowel (MacArter to MacCarter). The reverse also occurs. If the second name begins with a /k/ or /g/, producing two /k/ sounds together, one may disappear (MacGill to Magill; MacKenzie to MacEnzee). Mac is at times pronounced "muck" and written that way (Mac 'il Roy to Muckleroy).
Spelling differences among names are usually trivial no matter how much pride a person has in a particular version. Many of our ancestors were illiterate until recently, especially if they were Gaelic speakers. Most Gaels were not taught to read or write their own language. In contrast with English, Gaelic speakers place more emphasis on the spoken language than on the written form. This means that Gaelic spelling is constantly being modified to match the spoken form, the latest major revision in 1982. In addition, Gaelic speakers did not need or use family names until they began to interact with the English speaking culture. The Gaelic naming system is quite different and either shows a person's lineage or some personal attribute. "Donald of the race of Donald". "Donald, Son of John", and "Donny Little" all might be the same person.