Lewis Short
costum | costŏs, i (noun N.f) = κόστος: n. (access. form, like the Greek, , , f., Luc. 9, 917)
* An Oriental aromatic plant: Costus Arabicus, Linn.; Plin. 12, 12, 25, § 41; Ov. M. 10, 308; Hor. C. 3, 1, 44 al.; freq. used in the preparation of costly unguents,Plin. 13, 1, 2, § 15 sq.; 13, 1, 2, § 18; in offerings,Prop. 4 (5), 6, 5.for the preservation of fruits,Col. 12, 20, 5 al.
Charlton T. Lewis, Charles Short, A Latin Dictionary