Why do the English call the pound, a “quid”?

If you have friends from Great Britain or every seen any English folk talk together. If they talk about money they will often talk about the quid, not the pound.  It has often been related to the sovereign the most important gold coin in the history of transactions. One pound is equal to one hundred pence. When exchanged for something of the same exact value, the deal in latin is quid pro quo- something for something but later it was just cut short to Quid.

Did you know that the pound is the oldest currency that is still in use till this very day.