from The Century Dictionary.
Sorry, no etymologies found.
The bombers have been portrayed as so-called clean-skins - people with no history of extremism, people the intelligence services could not be expected to stop.
All the cattle running in the mountain gullies and on the spurs, had been brought in, the calves and "clean-skins" branded, and now there remained only those which roamed about the coast lands.
"There are any amount of wild cattle running in the ranges -- all clean-skins" (unbranded), "and no one claims them.