1. A day of stock market catastrophe. Originally, September 24, 1869, was deemed Black Friday. The crash was sparked by gold speculators, including Jay Gould and James Fist, who attempted to corner the gold market. The attempt failed and the gold market collapsed, causing the stock market to plummet.

2. The day after Thanksgiving in the United States. Retailers generally see an upward spike in sales and consider this to be the start of the holiday shopping season. It's common for retailers to offer special promotions and to open early to draw in customers.

1. The term "black" has been used to describe other disastrous days in financial markets. For example, on Black Tuesday, October 29, 1929, the market fell precipitously, signaling the start of the Great Depression. The largest one-day drop in stock market history occurred on Black Monday, October 19, 1987, when the Dow Jones Industrial Average plummeted more than 22%.

2. The idea behind the term "Black Friday" is that this is the day in which retail stores have enough sales to put them "in the black" - an accounting expression that alludes to the practice of recording losses in red and profits in black.