This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The character contains 髟 (hair) on top, suggesting a meaning related to hair, but the lower component's origin is unclear.
The top part 髟 looks like long hair, but the lower part is obscure. Without a clear meaning, it's hard to form a mnemonic.
For タ, imagine a tangled wig (タ) made of hair, since the top component 髟 suggests hair. The tangled wig cues タ.