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
cŏ-ĕpŭlōnus: i, m. epulo,
I a fellowbanqueter or companion at a feast, Plaut. Pers. 1, 3, 20.