Given that we've gone four pages without it, a reference to the actual source of the name could be useful.
Black Friday marked the time of the year when retailers would be 'in the black' after having made losses from July 1 through to that point. Thanksgiving being a holiday on a Thursday, it made for a good chance for retailers to have a promotion on the Friday as people would be likely to take a day off (to bridge between Thanksgiving and the Saturday, making it a four day weekend) and be free to do lots of shopping
Things have changed since it first came about (for example, the US fiscal year now starts on 1 October instead of 1 July, and businesses can now choose their own fiscal year) but the point still remains that the period between Thanksgiving and Christmas is the high point of the year for retailers.
If you don't want Black Friday in the UK, stop buying stuff from the USA.