@Nancy Drew I've been wondering lately too about this. I have a close friend named Karen and I feel sorry for anyone who has the name (like Debbie "Downer" too).
Why all of a sudden the use of Karen as the stereotyped name for an obnoxious middle aged white woman who has three children at home, is entitled and asks to speak to the manager (BTW, most Karens are Boomers and no longer have kids at home) ...at least that's the portrait that I have gotten from reading various sites online about it.
There's even an article in the NY Times on "Karen"!