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The names Brian and Bryan are now the male version of Karen ... because those names are plummeting in popularity, and the switch appears to be tied to 3 notorious owners of the monikers.

Admittedly, this would be rock bottom on the list of alleged crimes committed by Bryan Kohberger, Brian Laundrie and Brian Walshe ... however, a spokesperson for Babynames.com tells TMZ they're seeing a steep decrease in those names.

We're told since last August, not a single user added "Brian" to their list of favorites. While it had already been slowly decreasing in popularity -- it was considered "dated" from the 1970s -- it's now fallen off a cliff.

As for "Bryan," we're told it stands a little more popular, but has decreased by about 10 percent recently ... and it might be too early to see the full effects of the Idaho students case and the alleged quadruple murderer.

brian laundrie

No doubt, it's been an odd and ominous run for Brians and Bryans, going back to the summer of 2021 ... when Laundrie -- Gabby Petito's boyfriend -- murdered her while on a road trip. His remains were eventually found in a nature preserve in Florida where he died by suicide.

More recently, Idaho murder suspect Bryan Kohberger has been accused of gruesomely killing 4 college students, and is being held without bail until his trial this summer.

Brian Walshe mug shot Cohasset Police Department

Then there's Brian Walshe, who pled not guilty this week to killing and dismembering his missing wife, Ana.

While Walshe and Kohberger have yet to be judged in a court of law ... the court of public opinion seems to have a verdict on their first names.

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