Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
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).