Money given by a buyer to a seller to bind a contract WordNet 3.0 & Open English WordNet

An earnest payment or earnest money is a specific form of security deposit made in some major transactions such as real estate dealings or required by some official procurement processes to demonstrate that the applicant is serious and willing to demonstrate an earnest of good faith about wanting to complete the transaction. Wikipedia

kind of commitment fee Wikidata

Money paid as a deposit to show intent to buy or to reserve an item to be purchased; especially, money accompanying an offer to buy real estate. Wiktionary

Money paid. Wiktionary (translation)