This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
懞 combines 忄 (heart/mind) with 蒙, which likely contributes sound. The exact historical development is uncertain.
The heart radical 忄 beside 蒙 suggests a state of mind, but without a clear meaning, picture a heart covered by a hazy, unclear shape like fog: a confused or uncertain feeling.
For ボウ, imagine a bow (ボウ) of uncertainty: the heart is foggy, and you draw a bow in the dark, unsure of the target.