ἑξμέδιμνος
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)
ον,
A holding six medimni, Ar.Pax631.
German (Pape)
[Seite 884] von sechs Medimnen, Ar. Pax 631.