pterna denotes the heel in the clause describing someone lifting it against another.

The attested use names the heel as the body part lifted against someone in John 13:18.

1. Heel lifted against another · dominant

   In John 13:18, the accusative singular feminine form occurs in the clause about the one who eats bread and lifts a heel against the speaker; the APB renders the clause, “has lifted his heel against me.”

   John 13:18

In the Anselm Project Bible: In John 13:18, the APB presents the clause as “has lifted his heel against me.” The verse is read as a whole, but it explicitly includes “heel” in this clause.