ἀπερητύω
From LSJ
Δελφῖνα νήχεσθαι διδάσκεις: ἐπὶ τῶν ἐν ἐκείνοις τινὰ παιδοτριβούντων, ἐν οἷς ἤσκηται → Teaching dolphins to swim: is applied to those who are teaching something among people who are already well versed in it
English (LSJ)
[ῠ],
A keep back, hinder, A.R.1.772.
German (Pape)
[Seite 287] abhalten, ἀπερήτυε Ap. Rh. 1, 772.