Character Tui

It names a shed skin first, and shedding second.

The Eastern Han Shuowen Jiezi defines 蜕 as the skin cast off by snakes and cicadas, written with the insect radical. As a noun it is the cast skin; as a verb it means to slough it off.

Classical Chinese uses both senses, extended to leaving the body, death or release in religious writing. The shell itself appears as 蛇蜕 and 蝉蜕, with 蝉蜕 listed as medicine in the Bencao Gangmu; modern 蜕化 borrows shedding to mean a change in form, often for the worse.