淫
イン, ひた.す, ほしいまま, みだ.ら, みだ.れる, みだり
lewdness, licentiousness
JLPT0 G7 S11 F5000
The right-hand element# is 爪 claw/hand + 壬, here an abbreviated form of 妊 pregnancy → have (immoral) intercourse with a pregnant woman. 淫 adds 水 water (→ sexual fluids) → indulge heavily in immoral sex (compare 甚 and 耽) → be encompassed in *immorality* → *indecency*; *licentiousness*; *obscene*; *steep oneself in vice*. Note a variant form 婬 which replaces 水 with 女 woman.
[Full Kanji Etymology List]