πτέρνα

πτέρνα — ptérna

πτέρνα, πτέρνης, ἡ, the heel (of the foot): ἐπαίρειν τήν πτέρναν ἐπί τινα, to lift up the heel against one, i. e. dropping the figure (which is borrowed either from kicking, or from a wrestler tripping up his antagonist), to injure one by trickery, Joh 13:18 after Psa 40:10. (Often in Greek writings from Homer down; the Sept. for עָקֵב.)