Fish, I think the answer was across the street in another thread, or maybe even in one of the poker rooms here or there.
When a player in the old west may have had easily the best hand, he might not only put all his chips or money on the table, but he might bet his stagecoach or a wagon, as well. Since you can't put your stagecoach or wagon the poker table, you might just put in the nuts from the wheels.