The Gaelic word clanna means ‘children’ and that spells out its essence: a clan is a family. In theory, every Scottish clan is an extended family, with all its members descended from one original patriarch. Although clanship is based on blood affinity, a striking feature of the Scottish clans is their descent from totally different races. The MacLeods derive from Norsemen; the Murrays and Sutherlands from Flemish stock; the Bruces, Chisholms and Frasers from Normans and Angevins; and the royal house of Stuart from a Breton nobleman. In contrast, Clan Chattan and the MacMillans descend from old Celtic ecclesiastical office-bearers.
The Keiths traced their origins back to an ancient Rhineland tribe called the Catti. Sometime in the first century BC, so the legend goes, the Catti fought the Romans in the Hercynian forest: their retreat took them by Katwyck on the Rhine to embark for Scotland from the coast of Holland. Just how many Catti took to the boats in the exodus is not known but they eventually made landfall in Caithness or, as it was perhaps more recognizably known in first-century Scotland – Cattiness.
From the time they landed the Catti began to multiply significantly and adopted the local ways by joining the clan system as Clan Chattan. The clan spread throughout the north of Scotland and , as with all success stories of their time, what the Catti couldn’t win with the sword they won by marriage. Most of all they seemed to have had a sixth sense when it came to making a decision about which side to support in the wars and power struggles of the coming centuries. By this time the family name had changed to Keth or Keith.