The name itself is a piece of evidence: it was given by Gaelic speakers to neighbours who were not Gaels, and it records the survival of the Britons of Strathclyde inside a Gaelic-speaking Scotland.
Britons among Gaels
Galbraith comes from gall, a stranger or foreigner, and Breathnach, a Briton, so the sense is the foreign Briton or the stranger of British speech. In Gaelic the family are na Breatannaich and Clann a’ Bhreatannaich, simply the Britons and the children of the Britons. The distinction being drawn is between the Gaelic incomers of the early mediaeval west and the older Brittonic population of the kingdom of Strathclyde, whose language was closer to Welsh. Very few Scottish surnames preserve an ethnic observation of that kind, and it fixes the family firmly in the Lennox, on the ground between Loch Lomond and the Endrick where Strathclyde and Gaelic Scotland met.
The man reckoned first chief is Gilchrist Bretnach, whose byname is the same word, and who married a granddaughter of the first Earl of Lennox — a connection that places him in the later twelfth century and explains the family’s standing as one of the principal kindreds of that earldom. The early seat was Inchgalbraith, a small island in Loch Lomond a couple of miles south-east of Luss, with a castle on it. An island stronghold of that size says something about how the family held its position: not by numbers but by being difficult to reach.
Regents, and then a rebellion
The fourth chief, Sir William Galbraith of Buthernock, rose high enough to act as a co-Regent of Scotland in 1255, which is the outer limit of what a Lennox family could achieve. His son Sir Arthur, the fifth chief, came out for Robert Bruce and married a sister of Sir James Douglas. The Culcreuch branch in Strathendrick was established by 1320 and had inherited the chiefship before the century was out; the tower there is said to have been built about 1296 by a Maurice Galbraith.
The reversal came in 1425, when James Galbraith of Culcreuch, ninth chief, joined a rebellion that failed. The consequence was displacement rather than destruction: something like six hundred of the name went to Kintyre and to Gigha, which is why Galbraiths are an Argyll and island name as well as a Lennox one. The final collapse was financial and political rather than military. Robert Galbraith, seventeenth chief, ran the estate into debt and himself into the wrong political company, lost Culcreuch in the early 1620s, went to Ireland and died about ten years later. The year is not agreed: the clan account puts the loss of the castle at 1622, while the record of the castle itself has it sold in 1624, to a cousin, Alexander Seton of Gargunnock, in settlement of debt. The Napiers bought it in 1632 and held it for five generations. Robert’s grandson, the nineteenth chief, was the last of the line.
One sett under four surnames
The pattern sold as Galbraith is also recorded under the names Russell, Mitchell and Hunter. That is not a coincidence or a copy; it is the ordinary result of the way tartans were allocated to surnames in the nineteenth century, when weavers and pattern books were matching existing setts to names that had no documented pattern of their own. A sett shared between four unrelated families is a sett that was assigned rather than inherited, and saying so is more useful than pretending otherwise. It does not make the pattern less legitimate to wear under the Galbraith name; it does mean the pattern is not evidence of anything about the mediaeval family. Modern, Ancient, Weathered and Muted are dye conventions applied to one arrangement of threads, not separate designs.
Wearing a tartan that has no chief behind it
Galbraith is an armigerous name: a chief was once recognised, the line failed in the seventeenth century, and no chief of the name is recognised today by the Court of the Lord Lyon. In strict terms that means nobody has the authority to declare any pattern the official Galbraith tartan, since that power belongs to a chief. The heraldic identity survives in the crest badge, a silver bear head muzzled in blue, and in the motto Ab obice suavior, gentler for the obstruction, which turns a line of Ovid round to suit the muzzled bear.
The practical position is straightforward. No Scottish tartan is restricted by law, there is no register of who may wear one, and with no chief there is not even a courtesy to observe. Anyone of the name in its various spellings, including those descended from the Kintyre and Gigha lines and from the tenantry of the Lennox, has as good a claim as anyone can have. The Clan Galbraith Association exists to keep the history and the connections together, but it does not and cannot license the sett.
Sources: Wikipedia, Clan Galbraith, Culcreuch Castle, Armigerous clan and Scottish clan.