Lewis & Short

2. pessum, i, n. (collat. form pes-sus, i, m., Plin. Val. 1, 5 fin.; Theod. Prisc. 2, 5), = πεσσόν, πεσσός, in medic. lang., a pessary, App. Herb. 121; Theod. Prisc. 3, 5 (in Cels. 5, 21, written as Greek).