Aha, there was another on the shelf - “Baca,” it says, with the long A marked in the first syllable.
In my Hebrew Bible it’s just a Beth and a Caph, with a shewa (sort of) under the BEth and a long e mark (I forget the names, it’s been 30+ years) under the Kaph.
Not a lot to go on. WHich is no doubt why the translations vary. The RSV notes says “an unknown valley ...”