Money - MOney

Money was one arguably the most important invention. Money has been independently invented at one time or another in each important civilization. There is the concept of money has evolved in different times in history and in different parts of the world.

Historically, money has usually gone through four stages. In the first stage, money is made of a rare material, and the value of the money is determined by the amount of the material it contains. In the second stage, money is made of another material, such as paper, exchanged into the physical stuff. In the third stage, money cannot be exchanged into anything physical money. 

http://projects.exeter.ac.uk/RDavies/arian/money.html