All great points which shows that some of you know quite a bit about the jolly ol elf, his heritage and history...or you indeed have FAR too much time on your hands and reasearch each of your posts.
However, I fear every one of you are wrong. I will admit that you would be correct if we were talking about the kilt for who Santa WAS. But think deeply about who Santa IS.
Last time I saw Santa, he was wearing the Dress MacPherson Tartan