Wikipedia says:
“Although Black Friday, as the first shopping day after Thanksgiving, has served as the unofficial beginning of the Christmas season at least since the start of the modern Macy’s Thanksgiving Day Parade in 1924, the term “Black Friday” has been traced back only to the 1960s. The term “Black Friday” originated in Philadelphia in reference to the heavy traffic on that day. More recently, merchants and the media have used it instead to refer to the beginning of the period in which retailers are in the black (i.e., turning a profit).”
According to financial forecasters though, this year’s Black Friday, may be closer to light grey.
-PK