Start with the most obvious for a kilt site; the myth that the tartans are ancient, dating back to Roman times at least, and every clan had their own and used it as the primary way to tell who was who. Subvariations on this would include the various legal penalties for wearing a tartan not of your clan, the symbolism of colors in a tartan (e.g., red in a tartan indicates that the founder was illegitimate), and other general silliness about the tartan.