Animals, especially cattle, that have no brand or ownership mark on their skin; informal term for a person with no criminal record.
From clean (unmarked, unblemished) plus skin (surface). Australian colonial origin from livestock ranching, where unmarked animals ('cleanskins') could legally become property of whoever found and branded them.
In Australian history, cleanskins were basically free cattle if you could catch them—this actually created a wild and dangerous job because you had to run through the outback wrestling unmarked cattle. It became slang for 'person with no record' because like a cleanskin animal, they had nothing marked against them.
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