What is the TRUE origin of the term "Black Friday" in retail?

Black Friday marks the beginning of the holiday shopping season in many countries, but the linguistic origins of this retail phenomenon are often misunderstood. This linguistic retail trivia tests your knowledge about how language and commerce intersect in one of the world's biggest shopping events. Do you know the true etymology behind the term that now defines post-Thanksgiving commerce?

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It refers to retailers' accounting practices, where profits were recorded in black ink (vs. losses in red), as stores finally moved from loss to profit for the year.
It originated from the Philadelphia police in the 1950s, describing the chaotic traffic and pedestrian congestion that occurred the day after Thanksgiving.
It comes from the Old English 'blæc frīgedæg', meaning 'blessed shopping day', which evolved linguistically over centuries.
It derives from a stock market crash on Friday, September 24, 1869, when financial panic set in after gold prices plummeted, creating a retail disruption.