When I first heard "TERF" years ago, I understood it to mean radical feminists (who I didn't know anything about, but thought were unnecessarily extreme) who were bigoted and pointlessly hateful towards innocent people just trying to live their lives.
More recently, after realising I'd now be considered a terf, I thought, well, the meaning has changed, it's meaningless now, it could mean anything and anyone.
But... while the term is being thrown around by people who don't seem to realise what the letters even stand for, and it is being used in ways it maybe wasn't before (eg. any actual lesbian is automatically a terf), I'm not sure the intended meaning has really changed all that much.
Wasn't "TERF" always supposed to bring to mind the most hateful (female) creature you could imagine; someone who delights in casting others out and causing pain for no reason at all? And wasn't the reality behind that description always women daring to stand up for and protect themselves and other women from male intrusion and violence?