I was wondering about it too, but apparently it come from George Cukor’s 1944 film “Gaslight”. In the movie, a man is doing nefarious things that cause the gaslight (the kind of lighting they had) to flicker. His wife notices, but he tries to convince her that is it all in her imagination.

So Gaslight the movie, translates to “gaslighting.” Which is trying to convince you that things you absolutely know are not true.

But the article offers more information. Specifically how to spot and defeat gaslighters at your workplace. Frankly, I would quit a job with these kinds of gaslighters (or perhaps just fire them).

‘Gaslighters have two signature moves’: Are you being gaslighted at work? Here’s how to recognize the signs.