unlined clothes, light overcoat
褧 centers on a light, unlined garment worn as an outer layer, like a simple overcoat or thin robe.
褧 combines 衣 (clothing) with 耿, which likely contributes the sound. The character originally referred to a type of unlined garment.
The bottom part 衣 means clothing, and the top 耿 looks like an ear 耳 next to fire 火. Imagine a light overcoat so thin you can hear the crackling of a nearby fire through it.
For ケイ, picture a light overcoat made of thin KAY (ケイ) fabric, like a sheer summer robe.