Strong's G4418 · Greek

πτέρνα

pterna · pter'-nah

of uncertain derivation; the heel (figuratively)

Scholarly Lexicons

Abbott-Smith Manual Greek Lexicon

 1 πτέρνα , -ης, ἡ , [in LXX for עָקֵב ;] the heel : fig., ἐπαίρειν τὴν π. ἐπί , Jo 13:18 (LXX) .† 

G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain