This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 甹 is uncertain. It appears to combine 由 and 丂, but the original meaning and component function are unclear.
With no clear meaning, picture the top 由 as a reason and the bottom 丂 as a breath, like a sigh of uncertainty.
For ヘイ, imagine a person sighing 'hey' in confusion at the unknown meaning: hey -> ヘイ.