Past Potential.—The past tenses (usually the aorist, less commonly the imperfect) of the indicative with ἄν (κέν) denote past potentiality, probability (cautious statement), or necessity:
ὃ οὐκ ἂν ᾤοντο
ὑπό κεν ταλασίφρονά περ δέος εἷλεν
a. This is especially frequent with τὶς and with the ideal second person (cp.
b. The potential optative ( cross1829) in Homer refers also to the past.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].