Lewis & Short

plācāmentum, i, n. [placo], a means of pacifying or appeasing, a lenitive (postAug.): hoc veluti placamento terrae blandiuntur, Plin. 21, 7, 19, § 42.
In plur.: deŭm placamenta, Tac. A. 15, 44; id. H. 1, 63.