This is Charlie Willis's night herding song, according to Jim Bob Tinsley's book "He Was A'Singin' This Song". He worked for the Stadler Bros Ranch in Texas for some twenty years after the Civil War and made about ten trips from the home ranch to Wyoming to stock new ranches there.
He worked as the night hawk, the wrangler, for the crew. His job was to rope out the mounts every morning. Different outfits do this differently, but often it is the job of the wrangler to rope out the horse each cowboy will start the day with. He will "throw the hoolihan" for the outfit.
Also, in the earliest version of this, from Jesse Morris, who learned it from Charlie, collected by Alan Lomax in the '40's, there is a verse that says
Old Paint had a colt
Down on the Rio Grande
The colt couldn't pace
And we called her Cheyenne
Goodbye, Old Paint, we're leaving Cheyenne
Old time cowboys woulldn't try to break a horse until it was five years old or so. They were'nt considered strong enough to bear the weight or do the work. If the herd is bound for Wyoming and Paint has a colt that is weaned but not old enough to make the trip, (can't keep pace) it would be left at the home ranch. Mothers and colts will stay together for years in the wild. The song is about leaving Cheyenne, the colt, at the home ranch while Paint and Charlie go North.
Charlie is talking to Old Paint, who is reluctant to leave.
Least. that's how I explain it.