This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 畞 is uncertain. It appears to be a variant or related form of 畝, which represents a ridge or furrow in a field.
The kanji visually contains 田 (rice field) and a left side that looks like a person walking (夂) over a cross (十). Imagine someone pacing out furrows in a field, though the exact meaning is unclear.
For ボウ, picture a farmer bowing (ボウ) as they walk along the furrows in the field: bow -> ボウ.