dirty, pollute, disgrace, rape, defile
汚 centers on physical or moral impurity: something dirty, polluted, or disgraced. The more severe senses of rape and defilement are extreme applications of that same idea of violating purity.
汚 combines 氵 (water) with 亐, which likely contributes the sound and the idea of something bent or defiled. The character expresses impurity through the image of dirty water.
Water 氵 that has become bent or corrupted 亐 is dirty water. Picture a clear stream turning murky and polluted.
For オ, imagine a person exclaiming 'Oh!' in disgust when they see the dirty, polluted water: 'Oh!' -> オ.
dirty; filthy; foul; unclean
dirt; filth; stain; blot; spot
pollution; contamination
soiling; polluting; being dirty
corruption (esp. by a government employee); bribery; graft
to pollute; to contaminate; to soil; to make dirty; to stain
to get dirty; to become dirty
uncleanness; impurity; defilement
filth (esp. excrement, feces, urine); muck; waste; garbage; dirt; dust
bad name; bad reputation; disgrace; dishonour; dishonor; stigma; infamy
stain; blot; flaw; disgrace
filthy; dirty (looking); drab
filthy water; sewage
sludge; slime; dregs; mire
somehow dirty; slightly dirty; dingy
pollution; contamination; corruption; graft
dirty-looking; filthy; disgusting; squalid
filthy; unfair; dirty; untouchable; disgusting; nasty; foul; odious; repulsive
disgrace; shame
staining; spoiling; soiling; defacing; damage