The application of the name up-Rooter to a lawless mercenary is not unnatural.
"The Romance of Names"
Ernest Weekley
Imagine the hull of a North Shore ferry boat, blunted a little at the ends and cut off about a foot below the water-line, and parallel to it, then you will have something shaped somewhat like the hull of a Darling mud-Rooter.
"Over the Sliprails"
Henry Lawson
He had been a Rooter from the days of Underhand Pitching.
"Fables in Slang"
George Ade