μά asseverative (cp. μήν, μέν asseverative) with the accusative of the divinity or thing by which one swears. In negative sentences we have οὐ μά or μά alone with the accusative; in affirmative sentences, ναὶ μά, but more commonly νή. The omission of the accusative may sometimes be due to indecision or to indifference and not always to scrupulousness ( cross1596 c). μά means properly in truth, verily; but apparently governs the accusative after the ellipse of such verbs as
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].