This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 唕 is uncertain. It visually contains 口 (mouth) and 皁, but the original semantic and phonetic roles are unclear.
With 口 (mouth) beside 皁, imagine a mouth making a noisy, bustling sound, but the exact meaning is unclear.
For ソウ, picture a noisy soul (ソウ) shouting through the mouth 口 on the left: soul -> ソウ, and the sound is loud and restless.