ھ ی لh-y-l
(ض) هَالَ يَهِيْلُ هَيْلًاhāla yahīlu haylan (original form: هَيَلَhayala): (of sand) to flow and slide, (of a heap) to slip down.
مَهِيْلmahīl (passive participle, ism mafʿūl): flowing, sliding — i.e. sand that will not stay in the hand. A morphological point: مَهِيْلmahīl was originally مَهْيُوْلmahyūl (the passive participle, ism mafʿūl, of a hollow root (ajwaf) with yāʾ); the wāw was elided and the hāʾ given a kasrah. Only once in the Quran: ﴿وَكَانَتِ الْجِبَالُ كَثِيْبًا مَّهِيْلًا﴾ (Al-Muzzammil 73:14) — i.e. the mountains will become a heap of sliding sand.