I apologize for the delay in this letter. Here's the information we found about the name "Connar Matthew MacGlashan," which you'd like to use as a 12th-century name.
Before reading this letter, we recommend that you read the Web page "Scottish Names 101," which gives an introduction to issues in Scottish naming practices that will clarify many of our comments. The URL is
"Connar" looks like a modification of the name "Connor," which is an English version of the Gaelic name "Conchobar." We didn't find any examples of "Conchobar" from period Scotland, and as far as we can tell, it's an Irish name which wasn't used in Scotland. The pronunciation changed over time, but our best approximation is "kon-cho-war." "ch" here represents a sound not found in English which is hard to describe; it's found in Gaelic and in German.
"Matthew" is commonly found in Scots records (note that "Matthew" is a Scots name, not a Gaelic one). However, double given names (what we call a "first name" and a "middle name" were not used in Scotland until much later than the 12th century, and didn't become common until after our period. For a 12th-century name, you should only use one given name.
"mac Glashan" is a modern Scots and English rendering of the Gaelic name "mac Glaisein," which means "son of Glasein." "Glasein" is a short form of the name "Gille Ghlais" which developed sometime between the 13th and 15th centuries. So, the closest 12th-century form of "mac Glashan" would be "mac Ghille Ghlais."
We also wanted to let you know that "clan names" as used today are a purely modern invention. In period, a name like "Macdonald" meant "son of Donald," not "part of the Macdonald clan." Anyone in any clan with a father named Donald was likely to be called "mac Donald."
We can suggest the following options:
Our information on this name came from "The Surnames of Scotland" by George Black and "Corpus Geneologicum Hibernae" by M. A. O'Brien.
Talan Gwynek, Tangwystl verch Morgant Glasvryn, and Arval D'Espas Nord contributed to this letter.
Whichever option you pick, we would be happy to do further research and commenting for you.
Academy of S. Gabriel