Apparently the term “Black Friday” dates to the 1950s and has its origin in Philadelphia.

 

From the ERLC weekly (read the whole piece here:

The term “Black Friday” was coined by the Philadelphia Police Department’s traffic squad in the 1950s. According to Philadelphia newspaper reporter Joseph P. Barrett, “It was the day that Santa Claus took his chair in the department stores and every kid in the city wanted to see him. It was the first day of the Christmas shopping season.” Barrettt first used the term in the city’s newspaper, the Evening Bulletin, in 1961 to refer to the traffic problems on that day. Local merchants complained to police commissioner Albert N. Brown about the negative association of the term, so Brown released a press release describing the day as “Big Friday.” By then it was too late; the media had already started referring to the day after Thanksgiving as  “Black Friday.”