Verlan, like Lunfardo, often makes up basilect argot vocabulary by swapping syllables from the acrolect. A problem occurs when the slang term becomes too popular, and the process needs to repeat (without self-inverting) to invent a new cryptic term.

For instance, femme -> meuf -> feumeu, of which I regularly hear the second in my unhip rural area, but have not yet heard the third.

Argies reportedly have chambon -> boncha -> chabón.

I'll have to check up on the pronunciation of Berkeley Castle. We had a vowel shift a few centuries back and Berkeley is often pronounced "barclay" but not always. If the castle name uses the modern pronunciation then berk doesn't work!

Whatever the etymology, berk is considered no worse than jerk hereabouts (UK.)