The mouthbow is a chordaphone and the simplest of all stringed instruments with some history in Asia and North America, but mostly in Africa. Those used in the US by the Cherokee for instance are not well documented. African bows were more ornate and a bit more advanced(?) and you will probably find much more info on them.

Obviously they played a minor role in appalachian music and in recent years the work of Buffy St.Marie has brought it too more prominence.

Try a search on GOOGLE and see what you can find.

Spaw