If your Y-DNA match group has developed a strong geographic pattern this will allow you to research the primary sources of that location. The records in many areas in the north of Ireland, Argyll, the southern Hebrides, are remarkably intact, and if is very possible to find your ancestor listed in them and extract a genealogy from the traditional Gaelic method of recording surnames.
Keeping with the Gaelic custom a surname often appears in a format that carried short genealogy in them based on the derbhfine (said jerub-finn-ah). The derbhfine name contained four generations of the man’s family back to his paternal great grandfather. The derbhfine gradually gave way to a three generation format called a gelfine.
This naming practice was important in the Gaelic world because their society was one of caste and heredity. Gaelic society needed to know not only your name, but the names of your father, grandfather, and great grandfather. It provided the information needed to explain who a man was and the lands and rights of his family within his district and society. An example of Gaelic surnames from this time: a man named Dónall Mac Ailein Mhic Eáin had a son named Lachlan who took the name Lachlan Mac Dónaill Mhic Ailein Mhic Eáin. His surname is Mac Dónaill and the Mhic Ailein tells you who his grandfather was.
The use of clan surnames was not universal and was a form often found only on legal documents written by government officials. Clan surnames were used more by the oldest sons of landed families and these names functioned as a title as well as a name. However, by following the derfbhfine name you can accurately track your ancestor’s family back for many generations.
This does take some skill and at least some knowledge of Gaelic is required. The records are written in Gaelic, phonetic Gaelic (usually done by a Lallans speaking clerk), Latin, Lallans, and Lallan’s influenced English. For an example we will look at the descendants of a historical Argyll man, Donnchadh Rua Mac Ailín Mhic Eáin Riabhach of Dunamuck.
Here is an example of a derbhfine surname of one of his descendants in a primary source: “On 14 January of that year (1612), Archibald M’Eane reoch Vc Donchie roy Vc Lachlane was made principal to Walter Lamont son of John Lamont of Anaskeog.” The Cautioners listed were Giolla Easpuig Mac Dónaill Mhic Dhonnchaidh Rua Mhic Lachlainn and Lachlan Mac Dónaill Mhic Dhonnchaidh Rua Mhic Lachlainn. If we take the name of the principal we have “Archibald M’Eane reoch Vc Donchie roy Vc Lachlane” which allows us to identify this man back to his grandfather and connect him to Donnchadh Rua Mac Ailín Mhic Eáin Riabhach of Dunamuck. In Gaelic his name is “Giolla Easpuig Mac Eáin Riabhach Mhic Dhonnchaid Rua Mhic Loclainn.” Translated into English: “Archibald son of brindled John grandson of Red Duncan of the clan Lachlainn. Of interest, the clerk wrote the last name in this derbhfine as a clan surname rather than by his actual great-grandfather’s surname which was Ailean This was done because his grandfather, Ailean Mac Eáin Riabhach, was the Taoiseach of Clann Lachlainn in Glassary. The two Cautioners listed are of the same family and both carry “Mhic Dhonnchaidh Rua” in their names and the House of Dunamuch tag which positively identifies these men. The derbhfine surnames and Dunamuch House name allows us to connect the principal and the Cautioners to the historical figure Donnchadh Rua Mac Ailín Mhic Eáin Riabhach who was the Taoiseach of House Dunamuck, a sept of Clann Lachlainn in Glassary who ruled there from 1460s into the early 1500s.
Here is an example using the same family of the Gelfine format surname: Donnchadh Rua Mac Ailín’s oldest son and heir was Lachlann Mac Donnchaidh Rua. He appears in the Poltalloch Writs on 20 October 1547 in connection with a precept of clare constat. His name is written “Lachlan McDonche VcAllan of Dunemuck.” The use of the House name of Dunamuch and the gelfine name allows us to positively link this man with Donnchadh Rua Mac Ailín.
So take heart. If your DNA match group has provided you with a geographic area to focus on, it is possible to use primary sources to extract a real genealogy. You can use the Derbhfine and Gelfine surnames along with land transactions of merklands and pennylands to follow the trail of your ancestors.