Lewis & Short

quā̆drŭplo, no perf., ātum, 1, v. a. [quadruplus], to multiply by four, make fourfold, quadruple (post-class.), Dig. 4, 2, 14, §§ 1, 7: numerus quadruplatus, ib. 38, 10, 10, § 17; 47, 2, 50 pr.; Ambros. Apol. Dav. 5, 22.