You seem confused. I did not ask its purpose but for its definition.
R B Fuller references metal, shaped in half moon crescents, --or really horns of a bull--- found in Meditrerannean floor that he believe was one of early forms of money.
Minoan culture{ 2000 BCE } ---see Altantis/Crete-- worshiped the bull and most likely loaded their ships with this valuable, shaped metal, and traded instead of trying to haul around and trade since so much less messier than cows, calves, goats etc that may die before getting to another shore.
East India Company was first mutli-national corporation
..."These Dutch companies amalgamated in March 1602 into the
United East Indies Company (VOC), which introduced the first permanent joint stock from 1612 (meaning investment into shares did not need to be returned, but could be traded on a stock exchange)"......
Greenback, penny, nickel, dime, quarter etc are all money irrespective of their changing values for bartering/trading consumers living or killing goods.
If they have too little or no value, then another medium ---ex digita/crypto-- will take their place.