TSUMUGU · TOCFL 2 (est.) · 字
汙
汙 ＝ 氵 ＋ 亏
ㄨ · wū
adj/noun — dirty, filthy; to stain, pollute
字源 FORM — what the parts do
氵義water
亏聲yú — the donor, since shifted to wūa curved stroke, the old form of 于
IF≠yú → wū — the donor reading drifts hard off track
Water (氵) that does not move — the old sense is a stagnant, murky pool (濁水不流). 亏, the curl on the right (an old shape of 于), carries the sound, drifted from yú to wū. Standing dirty water gives the everyday filthy, to stain: 汙染、汙點.
故事 STORY — a scene to remember it by
一窪水（氵）不流，日子久了——髒了。
A pool of water (氵) that never moves, and in time — filth.
字源記憶法
意 · Meanings
(本義)濁水、汙水— stagnant dirty water
→髒、汙染— dirty; to pollute常用
⇒汙點、玷汙— a stain; to disgrace
(本義) original meaning · → ⇒ each arrow = one more step of extension