Emily Dickinson Lexicon

AGA, n. [Per. اَقْ and اَقَا ak and aka, lord, dominus, herus; also, sir, a title of respect; Tart. aha. Qu. the och in Beloch, and ak in Balak.]

In the Turkish dominions, a commander or chief officer. The title is given to various chief officers, whether civil or military. It is also given to great landholders, and to the eunuchs of the Sultan's seraglio. – Encyc.