What does the phrase "White Trash" mean? Is it racist? Against whom?

[Hoof Hearted]

Poll question: What does the phrase "White Trash" mean? Is it racist? Against whom?

I'll never forget when I was in college this girl who was probably my best friend at the time, she was from a solid middle-class family, she was a practicing feminist and definitely a liberal. Still, one day I told her about something that I had done for someone even more disadvantaged than I was even though I knew they would never know where it came from. I told her about it because we were in a conversation and I wanted her to understand that even people of limited means like myself usually tried very hard to give to others when they could. In other words, I wanted her to understand that those of us without silver spoons tied to our baby books had to rely on each other.

Her response? "How WHITE of you."

I was truly perplexed in every sense of the word. I had never heard that expression before. I think it's mostly because I had an obviously sheltered up-bringing and I'm actually not "white" in the American sense of the word but I do indeed usually "pass" for white. It's very confusing to others. It's just a fact of life for me. I'm sure many who saw me driving by in by truly hideous and sub-standard car assumed I was "white trash".

On the other hand, the first day I drove up in my future (extremely WASP) MIL's driveway in my AMC Gremlin with plexiglass and duct-tape for a back window the first thing she said to my husband was, "She's very pretty, what IS she?". He was baffled and horrified.

In the interest of simplicity I could have omitted my own experience, but I am anxious to hear yours, and what you think.