Lewis & Short

2. ăcus, ĕris, n. (also, ūs, f., v. 1. acus, III.) [kindred with acus, ūs, Goth. ahana, old Norse agn, old Germ. Agana], = ἄχυρον, the husk of grain and of pulse; chaff, Cato, R. R. 54, 2; Varr. R. R. 1, 52; 57; 3, 9, 8.