Quote Originally Posted by Planopiper
I understood that "tartan" referred to the weave - under 2 threads, over 2 threads. That weave gives the distinctive diagonals when 2 colors cross. Most patterns that you think of as plaid are over one, under one. Also, they're generally not symetrical. I know there were a few non-symetrical tartans, but they really seem to have been an exception, more than the rule, at least since Victorian times when tartans as we know them really came to be developed. I remember reading that the non-symetrical Buchanan tartan was really the result of a misprint in a book that it was listed in.
There is a web site about tartans/plaids (sorry don't know the link) that makes this claim. I actually said this (in an e-mail) to Matt Newsome about three years ago (not knowing the extent of his knowledge at that time) and he promptly shot me down. I assume that he knows more than I do, and probably more that that web site as well. However if you can find that link I would like it.

That site also had as evidence that some one (I think it was the king at the time) ordering several yards of plain blue tartan.

Adam