Aes
or more properly As. A Latin word of probably Arian origin, meaning both pure copper and a mixture of tin and cop- per. The term served afterwards in Rome as a generic word for every variety of money.
The earliest types of the Aes are called the Aes Rude or Aes Infectum,i.e., un- wrought copper. There was no monetary unit and the weight formed the basis of all exchanges.
Source: Frey's Dictionary (American Journal of Numismatics, Vol. 50, 1916)