Later, PR efforts purposely invented the incorrect, more positive “etymology” (which is a very popular urban legend and false etymology that was even in Wiktionary from 2008 to 2015) that the name was given because this day is supposedly the first day of the year on which retailers typically posted profits (‘in the black’) rather than losses (‘in the red’).[1]
It’s a fun notion but incorrect - https://en.m.wiktionary.org/wiki/Black_Friday