ρόπτρον

From LSJ

αἰθὴρ δ᾽ ἐλαφραῖς πτερύγων ῥιπαῖς ὑποσυρίζει (Aeschylus, Prometheus Bound 126) → The bright air fanned | whistles and shrills with rapid beat of wings.

Source

Mantoulidis Etymological

Ἀπό τό ρέπω, ὅπου δές γιά περισσότερα παράγωγα.