Money evolved from precious metal coins.

Kings and Emperors routinely robbed their populations by withdrawing high gold or silver content coins from circulation and replacing the precious metals with low value metals like copper, tin, lead, or wherever is cheapest available, coated by a precious metal layer so thin it rubbed off in days. The coins were made to look similar but were eventually almost worthless. Often the King or Emperor would not even accept their own coin for tax but demanded goods or gold instead.