An extended family, or a group of extended families with a known [not mythological] common ancestor/genetic bond, constitutes a clan. Several clans, however, are often a part of another “umbrella clan” of a completely different surname: the Clan MacDuff, Clan McGillivray and Clan McIntosh, for example, are all components (along with other clans) of Clan Chattan, just as there are similar “individual clans” that confederate to form Clan Campbell and Clan MacDonald, etc., who don’t have these surnames.
Question: does anybody know what the name of the “umbrella” clan is? (My understanding is that the umbrella clan would be to traditional Scots what a tribe would be to American Indians- the Muscogee or Creeks, for example, being composed of the Wind Clan, the Snake Clan, etc., each clan being composed of family units.)
Looks like your Wiki link has answered your question for you – it’s a confederation.
According to my copy of “Clans and Tartans of Scotland” - Robert Bain 1968 edition-
The Clan is the umbrella group, the family name is the Clan sept.
The septs could either be blood relatives of the same or different family name or, groups (or individuals) who had obtained protection from the clan.
Wilson is Clan Gunn sept Wilson
Abernethy is Clan Leslie sept Abernethy.
Duncan could be Clan Duncan or Clan Robertson sept Duncan.
There may be many variations - families are like that.
A confederation is more usually applied to several clans who have joined together for battle.
Clan Chattan was the best known and largest confederation of clans, and hence has a lot of surnames associated with it.
However, I tend to take the whole clan / sept thing with a grain of salt. A lot of the stuff about the Highlanders was only written down in the early 19th century, after the clan system had been broken, and those who were writing about it tended to romanticise it. In all likelihood, the alliances between different families were a lot more fluid than the rigid clan / sept divisions suggest. Local alliances, shifting political factors, and location in the country would all play a role in deciding which big family a smaller family would associate with.
For example, in those tartan guides, my mother’s family is listed as associated with both the Campbells and the Stewarts. Since the Campbells and the Stewarts were at each others’ throats for a good portion of the 17th and 18th centuries, that sounds bizarre, if you think of clans as a rigid set of family alliances. However, it appears that her family tended to support the Campbells in the early 17th century, when the Stewarts were in power. Then, for some perverse reason they switched to the Stewarts towards the end of the 17th century, when the Campbells were ascendent and the Stewarts on the run. (With genes like that, I stay out of politics…)
On a related note, most tartans are modern inventions (mid-19th century onwards), and aren’t nearly as rigidly assigned as some of those tartan books would suggest.