What HuntsvilleTxVeteran called “splits” was called “mumbly peg” by the kids I hung out with back in the 50s.
In fact, mumbly peg is the name for yet another game: rapidly sticking a knife between the fingers (see: http://www.makemeking.com/home/dares/381/Mumbly_Peg.html)
So which is the “real” mumbly peg? Your guess is as good as mine.