The person above is correct that is has been a thing since the 1950s, but for most of that time it was a relatively rare term used to refer to the UK's communist party (which hasn't even existed since 1991) and occasionally for hardline old-fashioned leftists in general, again mostly in the UK. It's only in the past couple of years that it got picked up by the internet and went everywhere, which is probably why you haven't heard of it. I'm from the UK myself and I haven't heard of it until recently.