I know what "Black Friday" is and how the phrase first came about.
What I would like to know is how the phrase evolved into "Black & blue Friday" which seems to have come about in very recent years.
Although I can make a guess, I have not found any clear cut explanation.
My guess is that the phrase slipped from black that depicts the crowds of people in the shops and streets on that particular Friday to black & blue to depict the bruises shoppers get from jostling in the heavy crowds.
First question: is my guess good? If not why do people say Black & blue Friday?
Second question: when (and how/where, if anyone knows) did the phrase first appear?
Best Answer
"Black Friday" originated because for some retailers it is the day that their accounts for the year become "in the black", that is, positive. There's a convention that positive numbers on accounting statements are written in black ink and negative numbers in red ink. (It's not the only convention. Another is to put negative numbers in parentheses. Accountants don't seem to believe in minus signs like most of the rest of us use.)
"Black and blue" is a commmon English phrase referring to bruises. Like, "The muggers beat him black and blue." While I haven't seen any etymological history, I think it's a safe bet that "Black and blue Friday" is, as you indicate, a joke phrase combining "Black Friday" with "black and blue" bruises. I think that's how almost all English speakers would take it.