flowing, vast
滂 centers on water in overwhelming abundance: a vast, flowing expanse. The two given meanings are closely linked, with 'flowing' describing the motion and 'vast' describing the scale.
滂 combines the water radical 氵 with 旁, which likely contributes the sound. The character is associated with the idea of water spreading or overflowing.
The water radical 氵 beside 旁 suggests water that spreads out in all directions, like a vast flood flowing across the land.
For ホウ, imagine a vast flowing river that you can hear from far away: the sound 'hoo' (like the wind) echoes across the water, cueing ホウ.
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