No, it's just a name that was randomly chosen by someone to give a name to an imaginary character that retail assistants knew all to well, the meme first started showing up like 5+ years ago now maybe even longer tbh,
It is a sweeping generalisation of an older woman who won't listen to what you the store clerk says, even though you work there and have more knowledge, they just refuse to listen, get angry over nothing important and ask to talk to the manager just to get what they want, cus they know it's like an instant get what I want button.
It's a pretty weak meme as they go, seems more like a troll meme nowadays and so many people are responding to it exactly how the people trolling them with it want them to act,
It's like a self fufilling prophecy, the more you push back against the Karen meme the more Karen like you become, getting angry and escalating issues that shouldn't be escalated cus why is it even important? People are just laughing at the people getting offended so it keeps feeding the fire.
I guess the Karen meme boils down to someone making mountains out of molehills, now that I'm writing it all out and thinking about it