This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
渹 combines 氵 (water) with 訇, which likely contributes the sound. The exact historical development and original meaning are uncertain.
The left side is water 氵, and the right side 訇 contains 言 (words) inside a wrapping shape. Imagine water rushing around a loud echo of words, but the meaning remains unclear.
For コウ, imagine a loud echo (こう) of words 言 bouncing across the water 氵: こう -> コウ.
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