Comment: The initial syllable vanished in the weak position in most languages, but is preserved in Tsakh., Rut. (uq̇ul,huq̇ul or q̇ul in different dialects) and Ud. (where bul < *buʔul < *woƛ̣ul; cf. also *woƛ̣V-rV > Ud. ber 'pillow'). The Archi form is an original locative and means 'under the head'; PL *ƛ̣ should have given Arch. ḳ, but has been preserved in this exceptional form as a result of assimilation with the sublative *-ƛ̣:. The word belongs uniformly to the 3d class (in Rut., Tsakh., Kryz. and Bud.)
See Талибов 1960а, 295; Лексика 1971, 107; Гигинейшвили 1977, 69.