Matt Wray in American Sexuality:
Whether they use the term white trash or not, most Americans are unaware of its long and ugly history. If you had to guess, you’d probably say that the term arose in the Deep South, sometime in the middle of last century, as a term that whites coined to demean other whites less fortunate than themselves. Yet most of what we presuppose about the term is wrong…
…The long and disturbing history behind the term white trash reverberates with meaning today. With us still are stigmatizing images of oversexed and promiscuous trailer trash women; tasteless jokes about white trash and incest; and a widely shared belief that all poor whites are dumber than the rest of us. The stigma of white trash remains an active part of our fevered cultural imagination and for too many Americans, it remains unchallenged. Those who use the term today would do well to consider its history.
More here.