COMMENT: Despite the uncertainty in reconstructing *-p- or *-b- (not unusual in root structures with two stops), the root seems reliable. In PN and PWC there occurred an assimilations: *č < *č̣ (under the influence of the subsequent labial). Otherwise the correspondences are regular.
The root is also spread in some other Daghestan languages as a loan from Avar (Darg. č̣aIbar 'floor') or Andian languages (Gunz. č̣abar 'clay').