my first impression is it's a play on unity, that they are already going, but he is saying start whenever he wants to? Still, I can't really tell if they are in motion already... and he is at the front. So I'm confused.
"I think the joke is that wagon masters would shout "Wagons, hooooooo!" to start the journey. So a non- union wagon master would be like a discount, inferior version and would get it wrong"