Lewis & Short

1. hau (also au), interj., an exclamation of pain or grief, Oh! ah! au, nullan tibi lingua’st? Plaut. Stich. 1, 3, 104; id. Cist. 3, 15; Ter. And. 4, 4, 12; 42; id. Eun. 4, 3, 14; id. Heaut. 5, 3, 13; id. Ad. 3, 2, 38; id. Phorm. 5, 1, 27 et saep.