astringent, harsh, rough, uneven
濇 centers on a rough, harsh quality that is physically or metaphorically astringent: something uneven, coarse, or puckeringly severe.
濇 combines 氵 (water) with 嗇, which likely contributes the sound and may relate to a harsh or rough quality. The exact historical development is uncertain.
Water 氵 beside 嗇, a shape that suggests something harsh or rough. Imagine water flowing over an uneven, stony bed, making it feel astringent and coarse.
For ショク, imagine a harsh, astringent shock of cold water: shock -> ショク, and the rough water makes you recoil.