%assiento%

‖n. [ Sp. asiento seat, contract or agreement, fr. asentar to place on a chair, to adjust, to make an agreement; a (L. ad) + sentar, a participial verb; as if there were a L. sedentare to cause to sit, fr. sedens, sedentis, p. pr. of sed&unr_;re to sit. ] A contract or convention between Spain and other powers for furnishing negro slaves for the Spanish dominions in America, esp. the contract made with Great Britain in 1713. [ 1913 Webster ]