I learned what I know in language theory classes at the University of California, a while ago, within the context of old english language(s) and dialects.
I believe I read recently in something or other ("How the Scots Invented the Modern World and Everything in It" ?) that "Scot or Scoti" was a Roman term meaning thieves. Seriously. Could have been in another book, the name of which escapes me at present, but if yer interested I'll dig up the citation, it's on my bedside table (I think, just got back from vacation and the blood alcohol level is still pretty high!) or in a box, or somewhere in the warren I call home...