The first gold coins appeared around 560 B.C. Over time it became a practice to store larger amounts of gold in warehouses. Paper receipts were issued certifying that the gold was on deposit. These receipts were negotiable instruments of trade and commerce which could be signed over to others. They were not actual currency but are a presumed forerunner to our modern checking system.
Gold is original money. It was money before paper receipts were issued. The paper receipts were not money. They were substitutes for real money. Today, all paper currencies are substitutes for real money.