The term "Black Friday" originated in Philadelphia. In the early 1960s, Philadelphia police griped about the congested streets, clogged with motorists and pedestrians heading to the Army-Navy football game and looking for deals post-Thanksgiving, calling it “Black Friday.”
According to History.com, Philly's biggest department stores tried to steer away from the negative name and call it “Big Friday,” but the rebranding didn’t stick.
The term “Black Friday” (in the retail sense) was coined in the 1960s to mark the kickoff to the Christmas shopping season.
“Black” refers to stores moving from the “red” to the “black,” back when accounting records were kept by hand, and red ink indicated a loss, and black a profit.