In Homer κατανεύω means "nod in assent" or the like e.g. Il. 1.514 (νημερτὲς μὲν δή μοι ὑπόσχεο καὶ κατάνευσον / ἢ ἀπόειπ’) while ἀνανεύω means the opposite, "nod in refusal" e.g. Od. 9.468 (ἀλλ’ ἐγὼ οὐκ εἴων, ἀνὰ δ’ ὀφρύσι νεῦον ἑκάστῳ, / κλαίειν).
A little googling told me that in Greece an upward nod/rising the eyebrows now, over 2500 years later, still means "no" and a downward nod still means "yes". Can someone who knows Greek culture confirm this?