ἐν πέτροισι πέτρον ἐκτρίβων → by grinding stone against stones
φᾰγέειν: καὶ φᾰγέμεν, Ἰων. καὶ Ἐπικ. ἀντὶ τοῦ φαγεῖν, Ὀδ.