Dictionary.net

Contracts. Anciently, among all the northern nations, shaking of hands was held necessary to bind a bargain; a custom still retained in verbal contracts; a sale thus made was called handsale, venditio per mutuam manum complexionem. In process of time the same word was used to signify the price or earnest which was given immediately after the shaking of hands, or instead thereof. In some parts of the country it is usual to speak of hand money as the part of the consideration paid or to be paid at the execution of a contract of sale. 2 Bl. Com. 448. Heineccius, de Antique Jure Germanico, lib. 2, §335; Toull. Dr. Civ. Fr. liv. 3, t. 3, c. 2, n.33.