腰
ヨウ, こし, うすぐ
loins, hips, waist, low wainscoting
JLPT2 G7 S13 F1306
要# waist/hips +
肉
flesh → *waist*; *hips*; *small of the back*.
腰
was devised to replace 要 after the latter acquired its extended meanings.
[Full Kanji Etymology List]