I’m taking this from Wikipedia, but it’s a summary of what I found on other sites.
In African-American culture, there is a history of calling difficult white women or those who “weaponize” their position by a generic pejorative name. In the antebellum era (1815–1861), “Miss Ann” was used. In the early 1990s, “Becky” was used. As late as 2018, before the use of “Karen” caught on, alliterative names matching particular incidents were used, such as “Barbecue Becky”, “Cornerstore Caroline”, and “Permit Patty”. Linguist Kendra Calhoun connects “Karen” stereotypes to the older “soccer mom”. …
A more pointed explanation, which involves race, is the expression originating among black people to refer to unreasonable white women. The term was popularized on Black Twitter as a meme used to describe white women who “tattle on black kids’ lemonade stands” or who unleash the “violent history of white womanhood”. Now defunct Bitch magazine described Karen as a term that originated with black women but was co-opted by white men. …
The term is generally used to refer to women, but The Atlantic noted that “a man can easily be called a Karen”, with staff writer David A. Graham calling then-president Donald Trump the “Karen in chief”. Similarly, in November 2020, a tweet calling Elon Musk “Space Karen” over comments he made regarding the effectiveness of COVID-19 testing became viral. Numerous names for a male equivalent of Karen have been floated, with little agreement on a single name, although ‘Ken’ and ‘Kevin’ are among the most common names used. The Jim Crow era male equivalent to Miss Ann was Mister Charlie.
IOW, the term was originally meant to be both racist and sexist, just as “Becky” was, although not in the way American culture usually defines those terms. When white culture landed on the term to describe a wider version of the behavior, it became deracinated, so it’s used on black women, and desexed, therefore available for application to men as well. That’s pretty funny, considered that it’s opposite to the way pejoratives usually form.
I’ve never used “Karen” but the objections to it are weak. Our culture - and I assume everybody’s - regularly turns names into descriptors. Sex in the City launched a million “She’s such a Samantha” memes. Dick has already been mentioned, as has Chad.
Since the word is used only for people who earn the term by their behavior, Karens are not a protected class. I also think that uses of the term are diminishing, so we’re probably two years too late on taking a stand. Let it be forgotten the way a zillion previous fad terms have been forgotten.
