wig
髢 centers on a hairpiece used to supplement or replace natural hair: a wig.
髢 combines 髟 (hair) with 也, which likely contributes a phonetic element. The character specifically denotes a wig or false hair.
The top 髟 shows long hair, and the bottom 也 looks like a stand or base. Imagine a wig placed on a stand, ready to be worn.
For テイ, picture a wig styled into a neat 'T' shape on a stand: T -> テイ, and the wig is perfectly arranged.
hairpiece; false hair; switch