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τὸ κοῖλον τοῦ ποδὸς δεῖξαι → show the heels, show a clean pair of heels, show the hollow of the foot, run away
πῆξε: Επικ. αντί ἔπηξε, γʹ ενικ. αορ. αʹ του πήγνυμι.