Money or goods given to bind an agreement; specifically in law, the payment of part of the price by the buyer of a commodity as a guarantee that he will uphold the bargain.
" If any part of the price is paid down, if it be but a penny, or any portion of the good delivered by way of earnest (which the civil law calls arrha and interprets to be emptionis venditionis contractae argumentum), the property of the good is absolutely bound by it. " --Blackstone, Commentaries (ii. 30).
" To constitute earnest the thing must be given as a token of ratification of the contract, and it should be expressly stated so by the giver. " Chitty, Common Law Practice (iii. 289).
" Argentum Dei, God's money, i.e., money given in earnest upon the making of any bargain. " Blount, Law Dictionary, 1670.
Source: Frey's Dictionary (American Journal of Numismatics, Vol. 50, 1916)