Black Friday?

That sounds like the day the stock market crashed. So why is it suddenly being used to describe the day after Thanksgiving when so many people go out Christmas shopping? This is a new wrinkle on the fabric of our crazy society which I had never heard of until this year. Friends, however, tell me that the term applies to the fact that although stores are very busy, sales are not that great until prices drop later in the season. So it appears that since the bottom line for retailers is not big enough, it is "Black Friday". As usual, it's all about money...money...money.