|"Old Stewball was a Racehorse" is an old song. I think Stewball must be a corruption of the term skewbald, which indicates a pinto horse that has white markings on any color other than black. Old Stewball had a mane of gold, so here he is as a sorrel. The skewbald pony I had as a kid was dark chocolate and white, with dark chocolate mane and tail. A black and white pinto is a piebald, which comes from the same root as magpie, a bird named for its white markings on iridescent black.