This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 冃 is uncertain. It appears as a component in characters like 冑, but its independent origin is not well established.
The shape looks like a simple cap or cover: the outer 冂 encloses two horizontal strokes, like a cloth draped over something. Think of it as a covering, but its exact meaning is uncertain.
For ボウ, imagine a bow (ボウ) tied around the cap-like shape to keep it in place: bow -> ボウ.