• 腰こし — waist; lower back
• 腰痛ようつう — lower back pain
• 腰椎ようつい — lumbar vertebrae
• 腰掛こしかけ — seat; stool
• 腰帯ようたい — lumbar belt / waistband
• 腰掛こしかける — to sit down (set oneself)

腰 combines the body radical ⺼（にくづき） “flesh/body” with the phonetic 要, which contributes the reading ヨウ and the sense of a central, essential part. Together they point to the body’s “core” area — the waist / lower back.