polished rice or millet
粺 centers on grain that has been refined: polished rice or millet, emphasizing the process of removing the outer husk to reveal the clean, edible kernel.
粺 combines 米 (rice/grain) with 卑, which likely contributes the sound and possibly the idea of low or base, referring to the husk that is removed during polishing.
The left side is 米 (rice), and the right side 卑 looks like a hand holding a tool. Imagine using that tool to scrape away the outer layer of rice grains, leaving behind polished rice.
For ハイ, picture a high-pile of polished rice: high -> ハイ, and the rice is so clean it shines.