This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
淈 combines 氵 (water) with 屈, which likely contributes the sound. The exact historical development is uncertain.
Water 氵 and 屈 (bend, yield) together suggest water that is bent or stirred up, but the exact meaning is unclear.
For コツ, imagine a water droplet hitting a rock with a sharp kots sound: kots -> コツ, and the water bends around it.