The idea of stores going “into the black” is as far as I can tell a fairly recent interpretation, probably dreamed up by someone high up in the retail industry to try to make the term sound happy and positive. It doesn’t make sense to me at all - why would stores expect to turn the whole year profitable on a day when they claim so much is being sold at deep discounts?
My mother worked retail for years and I learned the term “Black Friday” from her. It was not a cheery happy thought 
In Australia last year there were devastating bushfires that killed nearly 200 people, now referred to as Black Saturday. The reason they chose that name was because of the previous bushfire disaster that happened 70 years before, called Black Friday.
So to us that name has serious connotations, and is wasted on some stupid shopping sales day.
It’s been in common usage for 10-15 years. Prior to that, it was “the day after Thanksgiving” and the sales were “Post-Thanksgiving Sales.”
The past five years, it’s been turned from a shopping day into a shopping frenzy day. The stores love having people stampeding into them (even in cases where people are killed in the stampede.)
It’s a myth that it’s the biggest shopping day; that usually goes to the Saturday before Christmas (not sure about this year, when Christmas is Saturday).
In the previously mentioned song “Black Friday” by Steely Dan they mention Muswellbrook. Was that town involved in the Black Friday fire? The second verse of the song seems to be set in Australia.
Sure seems like it, doesn’t it? (49:40)
That does indeed appear to be what happened. Philadelphia-area merchants seem to have been stuck with a term (“Black Friday”) that they were unhappy with (because of its generally negative connotations). Unsuccessful in stamping out the term, it appears that they figured they’d just have to live with it and consequently sought to rehabilitate the expression by giving it an upbeat “back in the black [ink]” explanation.
Two pieces by reporter Jennifer Lin published in *The Philadelphia Inquirer *in the mid-1980s make clear merchants’ distaste for early uses of “Black Friday.” (It’s at the bottom of the message in the link below.)
http://listserv.linguistlist.org/cgi-bin/wa?A2=ind0804D&L=ADS-L&P=R7698
We’ve also spotted a usage of “Black Friday” with respect to the day after Thanksgiving coming out of either Baltimore or New York in 1951/1952. Here, factory management referred to it as “Black Friday” because of inevitable worker absenteeism on a day sandwiched between Thanksgiving and the weekend.
http://listserv.linguistlist.org/cgi-bin/wa?A2=ind0908A&L=ADS-L&P=R2555
It’s difficult to know whether this 1951/1952 “Black Friday” was an isolated, tongue-in-cheek usage or whether it co-existed with “Black Friday” as experienced by Philadelphia cops or whether it influenced coining of the latter. Still, that both preceded retailers’ “black ink” explanation causes one to be suspicious of the whole commonly offered “accounting practice” theory for the term’s origin.
Well, what day is the big one before Christmas? We have after-Christmas sales, too.
Muswellbrook is in New South Wales, northwest of Sydney. Black Friday (and Black Saturday) occurred in rural Victoria, surrounding Melbourne. So it doesn’t appear to be connected.
My current computer was $150 after Christmas, down from the original $500.
We (in Canada) don’t really have a “door busting” sale day before Christmas. Sales just seem to gain momentum from the beginning of November until pretty much Christmas eve.
And, as mentioned, boxing day is now officially the day to go line up at 5:00 A.M. for your plasma TV.
I hate the term “door buster” too. It’s said so cheerily in the ads, but what I envision is a mob of people who have lost all traces of civility as they pound on doors that can barely hold them back. Eventually, the combined weight of the crowd makes the doors “bust”, and the mob washes over the helpless employees who drew the short straw for greeter duty that day. The fact that people have actually died at minimum wage jobs because people were so fucking focused on getting bargains that they didn’t notice the human being they were trampling makes using the term “door buster” in a positive sense particularly ghoulish.