This interesting name, with variant spellings Galbreth and Calbaith, originated as a nickname for a member of the Briton tribe of Strathclyde settled among the Gaels. In gaelic the name is written Mac Gall Bhreathnach, from "mac", son of "gall", stranger and "Breathnach", Briton. It is likely that these Britons migrated northwards at the time of the Anglo-Saxon invasions. The surname is first recorded in the early 13th Century, (see below). In a Lennox Charter believed to have an earlier date, he appears as Gillescop Galbrad. It is interesting to note that the area of Lennox near Dumbarton was known as "the kingdom of the Britons" up to 1124. Three carucates of land in Lennox were granted by Maldouen the earl to William, son of Arthur, son of Galbrat in 1238 and circa 1246, one, Gillaspec Galbraith witnessed the grant of the lands of Colquhoune to one Umfridus de Kilpatrick, The first recorded spelling of the family name is shown to be that of Gillescop Galbrath, witnessed a gift to Campsie Church, which was dated circa 1208, in the "Episcopal Register of Glasgow", during the reign of King William, known as "The Lion of Scotland", 1165 - 1214. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.