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
uncīnus: i, m. 1. uncus,
I a hook, barb (late Lat. for 1. uncus), App. M. 3, p. 135, 39; Pall. Mart. 10, 29; Vnlg. Exod. 28, 13. —As adj.: hamus, barbed, Paul. Nol. Carm. 20, 270.