ἔργοισι χρηστός, οὐ λόγοις ἔφυν μόνον → a friend in deeds, and not in words alone
subs.
P. μῖλαξ, ἡ (Plat.).
The word is also found in Eur., Bacch. 703, and Aristophanes, Nub. 1007, but apparently with a different meaning.