ὁμηγυρίζομαι
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)
A assemble, call together, πρὶν κεῖνον ὁμηγυρίσασθαι Ἀχαιοὺς εἰς ἀγορήν Od.16.376 :—also ὁμηγύρειν· τὸ συνάξαι, Hsch.