ἀπειρόκακον

From LSJ

κοινὴ γὰρ ἡ τύχη καὶ τὸ μέλλον ἀόρατον → fortune is common to all, the future is unknown | fortune is common to all and the future unknown | fate is common to all and the future unknown

Source

Russian (Dvoretsky)

ἀπειρόκᾰκον: τό душевная простота, неопытность Thuc.

Lexicon Thucydideum

simplicitas, honesty, sincerity, 5.105.3.