The name, which has become a slang term for an overly demanding or entitled middle-aged white woman, is fast becoming the way of the pet rock -- extinct -- because parents know the name's become toxic.

Honchos at Babynames.com tell TMZ ... none of their millions of website users have added the name Karen to their favorite name lists in the past year, and over the past decade, they've seen a 75% decrease in popularity.

Karen is trending in the world of baby names, we're told, but for all the wrong reasons ... babynames.com says it's seen a 10-fold increase in searches for the meaning behind the name, but expectant parents are running for the hills ... no Karen's in their baby reveals.

The moniker was originally a Danish form of the name Katherine, meaning pure, but that reference is now dated and irrelevant. We're told Karen was most popular from 1938 to 1968, but it's seen a steep decline in the past two years, as more and more examples of "Karens" flood social media.