To revert to an earlier bit, Eddie Lang's roots. He was the consummate jazz accompanist, but the roots are definitely in Americanised popular European(Italian) dance music. The interface between jazz, folk and popular was always a shifting and kaleidoscopic thing. As has ben pointed out, Texas swing is a big source for this kind of guitar playing. If you listen to early New Orleans guitarists, for example, they don't tend to sound like Eddie Lang. But white dance musicians, eg Texas swing band rhythm section men, do tend to.