This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The modern form visually contains 艹 (grass) and 洴, but the original component relationships are unclear.
The top 艹 suggests a plant, and the bottom 洴 contains water 氵, hinting at a floating water plant. Picture a small green plant drifting on a pond.
For ヘイ, imagine a floating plant shaped like the letter H, swaying gently: H -> ヘイ.