Wow, the idea of Slytherin being "foreign" never occurred to me before! I always equated it with "slither," which I'm sure is deliberate on JKR's part, and that has quite an Anglo-Saxon sound. In fact, I just looked it up:
[Middle English slethren, variant of sliddren, from Old English slidrian, frequentative of slidan, to slide.] (http://www.yourdictionary.com/ahd/s/s0478200.html)
Gryffindor, on the other hand, has a French ring to me: griffon d'or. So one could make a case for that being the "foreign" house, I suppose!
Slytherin Etymology?
[Middle English slethren, variant of sliddren, from Old English slidrian, frequentative of slidan, to slide.] (http://www.yourdictionary.com/ahd/s/s0478200.html)
Gryffindor, on the other hand, has a French ring to me: griffon d'or. So one could make a case for that being the "foreign" house, I suppose!