Lewis & Short

oh, interj., an expression for the most various emotions of the mind—for surprise, both joyful and painful; for great pleasure or sorrow; for earnest wishing, admiration, aversion, etc.—oh! O! ah! oh, tibi ego ut credam, furcifer? Ter. And. 3, 5, 12: oh, iniquus es, id. Heaut. 5, 3, 8: oh perii! Plaut. Cas. 2, 3, 19: oh, probus homo sum, id. Most. 1, 3, 86.
Repeated, oh, oh, oh, as an exclamation of lamentation, Plaut. Capt. 2, 1, 6: oh, oh, as an exclamation of exultation, id. Most. 1, 4, 12 (al. oh, al. ohoho).