The term "trash" in reference to impoverished whites was actually coined by whites in the Antebellum South. The rich plantation owners looked down upon their unfortunate brethen and spoke disparingly of them as "poor trash." Even the slaves picked up on their venacular and used the term freely (though not in their presence). It's amazing that well over a century the phrase, though evolved, is still used. But then again, so is the term "N*****" by many including our own Americans of African descent.
BTW, the term "turn-key" in reference to deputies or correctional officers goes back several centuries and was used during Revolutionary War times.