My search of online sources for the origin and history of Black Friday allowed me the discovery of certain facts whose summary is as follows:
The phrase Black Friday was first used in 1961 by police in Philadelphia to refer to the heavy traffic, both pedestrian and vehicular, which would occur on the day after Thanksgiving.
The streets and shops would become overcrowded with people who began their Christmas shopping right after Thanksgiving, causing a frenzy and making both police officers and sales clerks dread the hard work on this day.
A popular explanation for the phrase Black Friday is that on this day retailers start to turn a profit, going from being in the red, meaning owing money, to being in the black, meaning not being overburdened by debt.
Happy Black Friday!