wig
髲 centers on a wig: artificial hair worn on the head.
髲 combines 髟 (hair) with 皮 (skin), suggesting hair placed on the skin or scalp. The exact historical development is uncertain, but the component combination fits the meaning of a wig.
The top 髟 is the hair radical, and the bottom 皮 means skin. Picture a wig made of hair sitting on the skin of the head.
For ヒ, imagine a wig made of heat-resistant hair: heat -> ヒ, and the wig stays perfect even when it's hot.