Being an American, where the idea of clans (or even genealogy in general) don't mean anything, I'm terribly confused about something.

All the research I've done on my mother's family (Kilpatrick) leads to Clan Colquhoun, where it is listed as a sept. But the history of Clan Colquhoun says this (quoted from the Wikipedia article):

"In the 13th century Maol Domhnaich, Earl of Lennox granted the lands of Colquhoun, located in Dunbartonshire, to Humphry de Kilpatrick. Humphry’s son, Ingelram de Colquhoun, who lived in the reign of Alexander III, was the first person recorded as taking Colquhoun as a surname."

So it seems that the Colquhoun name (or clan) did not even exist prior to this. Humphry's son took the name Colquhoun and magically sprouted a clan based on that name? And if so, where did the "lands of Colquhoun" come from, to be granted to Humphry? I can't find any history of Colquhoun before this, or how there were these "lands of Colquhoun" before Colquhoun existed as a name.

But my real question is why Kilpatrick is considered a sept of Colquhoun instead of something else. Since the name Colquhoun was first used by a Kilpatrick (and according to most purists, you can't just randomly change your name to identify with the clan you like; it must be given to you by your father), why would the clan not be called Clan Kilpatrick?

Either the rules concerning clan affiliation are more loose than the experts say they are, or I'm missing something. By rights, since the entire Colquhoun Clan history came from a Kilpatrick, wouldn't it be more appropriate for them to have kept that name?

Not that I expect them to change it now due to my sentiments, of course, but it does seem to disagree with what people claim is "proper". And being of the Kilpatrick line, I don't understand why Kilpatricks are seen as a sept to this clan when it was a Kilpatrick that was the first to take the Colquhoun name.

Can someone explain it to me? Is there some other history I haven't seen? I fully admit to knowing virtually nothing of the intricacies of the Scottish clan system and such.