εἰκοσάμηνος
From LSJ
οὕτω τι βαθὺ καὶ μυστηριῶδες ἡ σιγὴ καὶ νηφάλιον, ἡ δὲ μέθη λάλον → silence is something profound and mysterious and sober, but drunkenness chatters
English (LSJ)
ον,
A twenty months old, AP7.662 (Leon.).
German (Pape)
[Seite 727] von zwanzig Monaten, Leon. Al. 41 (VII, 662).