turbid, muddy
淟 centers on water that is not clear: turbid, muddy, or clouded with suspended particles.
淟 combines 氵 (water) with 典, which likely contributes the sound and may relate to the idea of something standard or settled, but the exact historical development is uncertain.
Water 氵 mixed with a standard 典 reference becomes muddy: imagine a clear standard being stirred into water until it's turbid.
For テン, picture a ten-gallon bucket of muddy water: ten -> テン, and the water is so turbid you can't see the bottom.