This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
汒 combines 氵 (water) with 亡, but the exact historical development and original meaning are uncertain.
Water 氵 beside 亡, a shape associated with loss or disappearance, could suggest water vanishing or a vague, indistinct flow. Without a clear meaning, treat it as a shape to recognize.
For ボウ, imagine a bow floating on indistinct water: bow -> ボウ, and the water makes the bow's reflection vague and uncertain.