rice grits left after hulling
糏 centers on the broken, powdery rice fragments left after hulling: rice grits or coarse rice powder.
糏 combines 米 (rice) with 屑 (scraps, fragments), suggesting rice that has been broken into small pieces or grits. The exact historical development is uncertain, but the component relationship is clear.
Rice 米 that has been reduced to scraps 屑: imagine hulling rice and being left with a pile of broken rice grits.
For セツ, picture a set of sieves used to separate the rice grits: set -> セツ, and the sieves sort the broken rice.