"For those unfamiliar with American customs, Black Friday in the US refers to the day after Thanksgiving Day, which is traditionally considered the first day of the holiday shopping season. It's generally the busiest shopping day of the year, resulting in huge profits for retailers – thus, putting them 'in the black.'"

This is not why it's called Black Friday. It's called Black Friday originally by the retail workers who had to man the stores that day. "Black" meaning bad or dark, in this case, like "this is a black day", rather than any reference to finance (or racism). Those who worked their way into the corporate structure of many retailers, or graduated college and moved on in their careers retained their floor-worker slang, and the term spread.