濁る
にごる · nigoru · JLPT N2 · verb-godan
to become muddy
💧 濁 = 氵 (water radical) + 蜀 (sound part): a water word for water that has turned murky
The water radical 氵 shows this is about liquid. Nigoru also means impure or cloudy, and the same verb gives the name 濁点 (dakuten) for the mark that voices a consonant.