A little pedantic, but it's worth mentioning that the assumption here is _spoken_ languages. There's a whole set of sign languages around the world as well.
I think that would also be something interesting to look into as well! Not only are spoken words borrowed, but so are signs and simple gestures. I guess you'd have to make some delineation about where the line in the sand is, since a smile could be considered a sign, and is probably (no evidence) nearly universal. Still interesting though.
If you ever wanted to do a little research on something like that, I'd read your write up.