汚れる
よごれる · yogoreru · JLPT N4 · verb-ichidan
to become dirty
🧦 汚 = water 氵 + a hollow: stagnant water turns foul; yogo sounds like yuck-o
The kanji 汚 pairs the water radical 氵 with a part meaning a hollow or dip, so the idea is standing water going foul. The れる ending marks it as happening by itself: something gets dirty. Compare 汚す (yogosu), to make something dirty.