Derivation of "Black Friday"

A news report on the BBC network explained that the "Black" in "Black Friday" referred to the start of the holiday season which enabled merchants to stop losing money (in the "red" since losses in hand written ledgers were designated with red ink) and start making money (thus in the "black".)

Here we thought "Black Friday" referred to the dangers and frustrations of trying to wait on or be among hordes of shoppers.