The Collaborative International Dictionary
Assiento \As`si*en"to\, 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?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.
Douglas Harper's Etymology Dictionary
1714, "contract between the King of Spain and another power" (especially that made at the Peace of Utrecht, 1713, with Great Britain for furnishing African slaves to the Spanish colonies in the Americas), from Spanish asiento, from asentar "to adjust, settle, establish," literally "to place on a chair," from a sentar, from Latin sedens, present participle of sedere "to sit" (see sedentary).
Wiktionary
n. (context historical English) A contract or convention between Spain and other powers for furnishing Negro slaves for the Spanish dominions in America, especially the contract made with Great Britain in 1713.
Usage examples of "assiento".
The Assiento of negroes was at this time held by two Genoese named Grillo and Lomelin, and with them the English ambassadors several times entered into negotiation for the privilege of supplying blacks from the English islands.
He granted an exclusive privilege to the English for furnishing the Spanish West Indies with negroes, according to the assiento contract.
The frequent possession of Assientos by the Portuguese and Dutch in the first half of the seventeenth century also facilitated this contraband, for when carrying negroes from Africa to Hispaniola, Cuba and the towns on the Main, they profited by their opportunities to sell merchandise also, and generally without the least obstacle.