The functions of deposit and loan have ancient origins: individuals used to entrust their assets to the treasure of the temple and priests already during the Sumerian Age, in Mesopotamia and among the ancient Greeks. In medieval times, in addition to the normal functions of providers, custodians and money-changers, bankers also took the guarantors of payments, signing letters of credit which undertook to pay sums on behalf of those who brought it: that was the first appearance of cheques, which relieved merchants and sovereigns of risk to carry large amounts of cash or valuable goods. This new activity collected so successful (and was so profitable) to create immense fortunes: in the largest commercial cities of Europe families of bankers became rich and powerful, so get to lend money to the kings of Europe, by financing their wars. Very often, rather than repay the loans, some of those creditors offered as payment feuds and noble titles.

Originally, commercial banks developed by the goldsmiths, who guarded gold and other precious objects of their clients , give them back when requested by issuing a receipt in exchange. Little by little the goldsmiths realized that people were willing to accept a quantity of gold in a given value and not the same gold that had actually deposited. They also understood that people did not withdraw all together gold deposited. Each day a part of gold was withdrawn while other gold was deposited. The balance between deposits and withdrawals, under normal economic conditions, was positive and then it was possible to make available to clients only a little part of gold deposited, using the remainder for interest bearing investments.