What is "unslings"

Usage examples of "unslings".

Finally Dancing Dan unslings the sack on his back, and takes out his package, and unties this package, and all of a sudden out pops a raft of big diamond bracelets, and diamond rings, and diamond brooches, and diamond necklaces, and I do not know what else in the way of diamonds, and Dancing Dan and I begin stuffing these diamonds into the stocking and Good Time Charley pitches in and helps us.