Why is a truck drivers helper called a swamper?

It's an old term that comes from the logging industry. The swampers were the young guys that got to crawl around in the underbrush and the swamp, cutting the limbs off of the trees and cutting the tree up into sections, and rolling the logs to the loading spot and helping load them. As opposed to the feller, who was usually the old guy with the brains who picked which tree to cut and could drop them in the right spot, or the drover who operated the team of horses.