The earliest reference I've found to "Stewball" by that name:

Atlanta Journal (June 28, 1931):

"Slaves wus bettin' and singin'

Stewball was a racer,
Mollie was, too."


And neither Oxford nor Merriam-Webster distinguish "lay" from "bet."

"Lay" is from the 14th century, to "bet" from roughly 1600.