This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
泩 combines 氵 (water) with 生, but the exact historical development and original meaning are uncertain.
Water 氵 beside life 生 suggests something like water giving life or a rising tide, but the actual meaning is unclear.
For ソウ, imagine a soul (ソウ) rising like water: soul -> ソウ, and the water radical 氵 gives life 生.