αείκαρπος
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
ἀείκαρπος, -ον (Α)
αυτός που διαρκώς καρποφορεί, παράγει καρπούς.