Strong’s Greek
G4974 — sphuron
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
σφυδρόν
sphuron — pronounced sfoo-ron'
neuter of a presumed derivative probably of the same as sphaira (a ball, "sphere"; compare the feminine sphura, a hammer); the ankle (as globular):--ancle bone.
1 occurrence in the KJV.
Acts 3:7
And he took him by the right hand, and lifted him up: and immediately his feet and ankle bones received strength.