Origin of the name "Black Friday"
The earliest uses of "Black Friday" come from or reference Philadelphia and refer to the heavy traffic on that day, an implicit comparison to the extremely stressful and chaotic experience of Black Tuesday (the 1929 stock-market crash). The earliest known reference to "Black Friday" (in this sense), found by Bonnie Taylor-Blake of the American Dialect Society, refers to Black Friday 1965 and makes the Philadelphia origin explicit:
JANUARY 1966 -- "Black Friday" is the name which the Philadelphia Police Department has given to the Friday following Thanksgiving Day. It is not a term of endearment to them. "Black Friday" officially opens the Christmas shopping season in center city, and it usually brings massive traffic jams and over-crowded sidewalks as the downtown stores are mobbed from opening to closing.[7]