Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ĕhem, interj., an exclamation of joyful surprise, ha! what! ehem, optume! quam dudum tu advenisti? Plaut. As. 2, 4, 43; id. Most. 3, 2, 38; id. Mil. 4, 9, 5; id. Rud. 3, 5, 25; Ter. And. 2, 5, 6: ehem, pater me, tu hic eras? id. Eun. 1, 2, 6; 3, 2, 9; id. Ad. 1, 2, 1; App. M. 2, p. 124, 29.