noun
ankle; ankle bone
Common everyday word for the ankle; the technical term malleolus is rarely used outside medical contexts.
転んでくるぶしをひねった。
I fell and twisted my ankle.
くるぶしのあたりが少し腫れている。
The area around my ankle is a little swollen.
足首 is a more formal or anatomical term for the ankle joint, while くるぶし often refers specifically to the bony protrusion.
The origin is uncertain; it may be a compound of くる (possibly related to 繰る 'to wind' or 枢 'pivot') and 節 (ふし) 'joint', but this is speculative.