Condictio certi
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
An action which lies upon a promise to do a thing, where such promise or stipulation is certain, (st certa sit stipulatio.) Inst. 3, 16, pr.; Id. 3, 15, pr.; Dig. 12, 1; Bract, fol. lOSb.