disc▪ The word obviously belongs to the complex, treated under ↗ḤLː (ḤLL) and ↗ḥalla (ḥall), of ‘to loosen, release’ and means a canal or an opening through which liquids, air, etc. are ‘released’ or run freely. Since no cognates are known from other Sem languages, the value seems to be a peculiarity of Ar. The fact, however, that it is found in EgAr and Yem dialects, with quite different specialisations, suggests an older origin.
▪ For the wider context of ‘to untie, release, purify’, etc., cf. ↗ḤLː (ḤLL) and ↗ḥalla (ḥall), with further references.