noun
Refers to the lower back and hip area. In everyday use, it can mean the waist or the general pelvic region, depending on context.
重いものを持ち上げるときは、腰を痛めないように気をつけてください。
When lifting heavy things, be careful not to hurt your lower back.
彼女は腰に手を当
She stood with her hands on her hips.
noun
body; resilience; springiness
Describes the firm, springy texture of food (especially noodles), hair, or paper. Often written in katakana as コシ in this sense.
See also: コシのある
このうどんはコシが強くておいしい。
These udon noodles have a nice firm texture and are delicious.
この紙はコシがあって折り曲げにくい。
This paper has a lot of body and is hard to fold.
ウエスト refers specifically to the waist measurement or the narrowest part of the torso, while 腰 covers the lower back and hip area more broadly.
弾力 is a general word for elasticity or resilience of any material. 腰 (in the 'body' sense) is more specific to the firm, springy quality of food, hair, or paper.
The historical derivation is uncertain. The kanji 腰 is conventionally associated with the lower back and hip area, and by extension with the idea of 'core strength' or 'body' in textures.