Cash was invented by its namesake, Johnny Cash.
Seldom used today, it was intended to be an alternate form of payment, as opposed to buying on credit or pulling out a gun. Pieces of metal and paper were assigned various values. Surprising as it may seem, this required the skills of counting, addition and subtraction, forgotten today.
Banks once held piles of cash, if you can believe that. Nowadays, if you go into a bank and ask for cash, you'll just get laughter. It's all for the better, as no one there would be able to count the cash.
Note the bulky metal object located on the front counter of many stores. That is a cash register, also invented by you-know-who. It is very heavy so that front counter will not fall over in an earthquake or high winds. Today, they are used to store credit card receipts, patrons' lost keys and pet mice. If a shopkeeper lets you look inside a register, you will find various dividers that once held those pieces of metal and paper mentioned earlier.