ὁ πατρὸς πρὸς μητρὸς πάππος

From LSJ

τὸ ἐγδοχῖον τοῦ ὕδατος καὶ τὰ ἐν τῆι πόλει ὑδραγώγια → the water reservoir and the conduits in the city (or on the acropolis)

Source

Greek > English (Woodhouse)

maternal great-grandfather