Assiento (Assien`to) , a treaty with Spain to supply negroes for her colonies, concluded in succession with the Flemings, the Genoese, a French company, the English, and finally the South Sea Company, who relinquished their rights in 1750 on compensation by Spain.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Asser, John * As`signats