COMMENT: A reconstruction *ɦărq̇wĔ is also possible (note that Lak. u-t:u- < *q̇ʷV-t:u-, as shown by an old Arch. loanword q̇ʷa-t:u- 'wide'). The initial weak syllable with laryngeal was dropped in PA and Lak., replaced by a reduplication syllable in PTs, and by class markers in Darg. and early WC (whence PWC *b-). In general the root seems quite reliably reconstructable for PNC. See Абдоков 1983, 144.
