What is the origin of the dollar sign ($)?
Many suggestions have been made about the origin of the dollar symbol $, one of the commonest being that it derives from the figure 8, representing the Spanish 'piece of eight'. However, it actually comes from a handwritten 'ps', an abbreviation for 'peso' in old Spanish-American books. The $ symbol first occurs in the 1770s, in manuscript documents of English-Americans who had business dealings with Spanish-Americans, and it starts to appear in print after 1800.
The word 'dollar' itself derives from the Flemish or Low German word daler (in German taler or thaler), short for Joachimstaler, referring to a coin from the silver mines of Joachimstal, in Bohemia (now Jáchymov in the Czech Republic). The term was later applied to a coin used in the Spanish-American colonies and also in the British North American colonies at the time of the American War of Independence. It was adopted as the name of the US currency unit in the late 18th century.
See other Questions about symbols.
Take a look at: What is the origin of the pound (£) sign?
Or: Does the '¢' in the US cent sign stand for 'cent'?