What is the Origin of the phrase its your turn in the barrel?

It is the punch line of a joke usually set in a logging camp or some other man camp with a barrel featuring a 2 inch diameter hole about 32 inches from the ground and a queue of men awaiting relief of backed up semen. A new man asks when he might join the queue and is told "any day but Thursday." He asks why and is told "Thursday is your turn in the barrel."