Toni Braxton, in a post on Facebook (see photo), suggested that the term “Black Friday” referred to the slave trade in the U.S., sort of a wholesale operation held before winter.

The singer’s accompanying post said that “slave traders would sell slaves for a discount to assist plantation owners” when they needed extra help to prepare for winter.
More recently and probably more historically, the term derives from the Friday before the annual Army-Navy football when it was held on the Saturday following Thanksgiving in Philadelphia.
The city became so crowded on the day before the game — and businesses so overwhelmed — that police dubbed it Black Friday.
Now, whether this had anything to do with black people and any racist connotation in the term is debatable. Anyway, it is now a term for the sales that take place on the day after Thanksgiving.
In retail operations, black refers to making a profit, as opposed to red, which means suffering a loss.