Traditional Scottish culture is mostly fictional
nysun.com
nysun.com
This is misleading. As noted later in the article, highlanders wore plaids, which are basically kilts with an over-the-shoulder piece that can be used as a cloak (it's actually all one big piece of cloth). If you saw a plaid, you'd say, "that's a kilt." Go to a Renaissance Festival and you'll see them all over the place.
P.S.
I am not even a little bit Scottish.
Yes, Beowulf. There were probably many others of its kind that were lost when the Anglo-Saxons became Christian. It would violate a lot of what we know about psychology if there were any culture that never had any indigenous mythology.
Not that I think it matters much: I suppose only those cultures that have existed entirely in isolation really have truly unique myths, and that isn't very many cultures. And maybe not all of those unique cultures, either, given how many themes are found in the mythology of very different peoples.
I would call it nationalism. Medieval Europe had no notion of nations. The Dutch national hero, for example, is Prince of Orange, a small sunny principality in South of France.
Throughout the history people associated themselves with their Sovereign, who could be a Spanish king in the Dutch case, or some German duke in case of Italians etc.
Then suddenly in the 19th century there was huge social demand for an independent nation-state. And that demand has met its supply in the form of national legend building.
Scots got their kilts (tartan originally was cloth supplied to colonies), Finns got their national epos written by a single guy, Russians got their national literature written by people who spoke French most of time.
An important lesson is that perception is reality and the one who controls (writes) the history can shape our self-identify.
In any case, Trevor-Roper published some of the papers this book was based on back in the 1970s and Boece's work wasn't the only record we have of that period of time.
But they do get drunk a lot.