I had never heard the term before I took a brief detour into retail, this occasioned by an ill-advised relocation in which my wife and I could not find jobs in our fields. I had never been terribly conscious of commercial life, always having had to be frugal out of necessity. I found the term bizarre until a coworker explained it to me, i.e., putting a business's books "in the black".
Working retail in an "entitlement culture" such as the United States is a hard way to make a living, but if you ever want to do a deep dive into human nature, it is an excellent school. When a society gets to the point where miscreants can just walk out of Walmart with stolen goods prominently in display, and the storekeepers aren't allowed to accost them and call the police, that's really sad.