straw raincoat
簑 centers on a traditional straw raincoat, a protective outer garment woven from straw or similar plant material.
簑 combines 竹 (bamboo) with 衰, which likely contributes sound and the idea of a covering garment. The character is associated with a raincoat made from plant material such as straw or bamboo leaves.
The bamboo top 竹 suggests plant material, and the lower part 衰 looks like a draped garment. Picture a raincoat woven from bamboo leaves or straw hanging down like a cape.
For サ, imagine a straw raincoat so light it feels like air: サ sounds like the first part of 'sah' in a sigh of relief when the rain stops.