Comments: The root is preserved independently in Ad. (PAK *ba 'many'; Kab. preserves it only within compounds like ba-ʁʷa-n 'to increase, prosper' - see Шагиров 1,70-71) and Ubykh. AT languages have kept the root only in compounds *macʷǝqA-bA 'thumb' (Abkh. a-načχǝ́-b, Abaz. mačʷqa-ba) and *š́acʷǝqA-bA 'big toe' (Abkh. a-š́ačχǝ́-b, Abaz. š́ačʷqa-ba) = Ub. q̇a(n)cʷa-bIǝ, ʎa(n)cʷa-bIǝ.
Another common WC compound with the same component is *ʎ́a-bIA "foot's bulge" > Ad. ʎa-b 'heel', Ub. ʎa-bIǝ (in compounds) - see Dumézil 1965, 235, Шагиров 1, 248-249).
On the etymology of PAK *ba see Шагиров 1,70-71 with literature (all attempts to separate this morpheme from Ub. bIǝ and AA *-bǝ seem to us superfluous).