A sept is a collection of people who hold the same surname, who are descendants of the original person who took that name.
Throughout the centuries, there were several small migrations of people from the Highlands of Scotland, but the coming of the Industrial Revolution led to many people being drawn to the big Scottish cities and from there a good number emigrated to Africa, Australia, Canada, New Zealand and the USA as well as to mainland Europe.
The range and variety of names connected to Clan MacThomas come about because people in early times were not able to read or write, let alone spell. If your name, or that of your mother, is one of the names shown in the box to the right, with the exception of Thomas and Thomson, then there is a distinct likelihood that your origins are Celtic and that your descendants came from the counties of Perthshire and Angus (and later Fife, Aberdeenshire and Kincardineshire). The prefixes "Mc" and "Mac" are interchangeable.
If your surname, or that of your mother, is Thomas or Thomson, then there is possibility that your forebears are Celtic, but further research (see under Genealogy) will be required to establish where they came from. If they are Scottish, not all with have come from the above mentioned counties in Eastern Scotland.
Here are a number of pointers which may be of assistance in determining whether you are a MacThomas and eligible to apply for membership of the Clan Society: