We got the $ from the Spanish. In the late 18th century, merchants in the North American British colonies traded mainly with two currencies: the British pound and the Spanish dollar. When the United States adopted its own currencyin 1785, it used Spanish money as its model—a deliberate "screw you" to the British. Scholars have since theorized that the $ sign evolved out of an abbreviation for peso: The plural for pesos was "ps," which eventually became "ps," and then simply an "S" with a single stroke denoting the "p." One early instance of the $ symbol crops up in a letter written by the merchant Oliver Pollock in 1778. Pollock also uses the "ps" abbreviation, making the letter a bridge between the two. The double-line through the S variation is less easily explained. Some believe they represent the twin pillars of Gibraltar depicted on the Spanish coat of arms. Others say it's shorthand for the letter "U" superimposed over the letter "S"—for U.S.
Other monetary symbols have more obvious origins. The sign for the British pound, £, evolved from the Latin word libra, meaning scales, since the British pound was originally worth exactly one pound of pure silver. The Chinese yuán and the Japanese yen—both of which mean "round object" in their respective languages—use the symbol ¥, based on the letter Y as transliterated by international traders. As for the euro: After soliciting designs from about 30 teams of artists, the European Commission polled 2,000 members of the public on a shortlist of 10 finalists and ultimately selected the €. (A German named Arthur Eisenmenger then claimedhe had designed the symbol decades earlier.)
Many countries don't bother to create their own symbols, relying on simple abbreviations instead, like zł for the Polish złoty, or DM for the former German Deutsche Mark. Others combine a letter abbreviation with the dollar sign, such as the Nicaraguan córdoba (C$). The symbol for the Israeli "new shekel," ₪, joins the first Hebrew letters of each word into one unit. It's common for currency symbols to change over time. The Russian ruble, for example, was originally represented with the Cyrillic letter " Р" written horizontally over a vertical " У." That later become a simple "R" or " руб."
While each country has its own way of representing its currency, there is also a standard international system known as the ISO 4217, established in 1978 by the International Organization for Standardization. These codes are used for banking and business transactions around the world and look a lot like stock ticker symbols: JPY for Japanese yen, RUB for Russian rubles, and INR for Indian rupees. Even more abstract is each currency's numeric code, which usually matches its country code as established by the ISO. The numeric code for the Saudi riyal, for example, is 682.
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Explainer thanks Robert Hoge of the American Numismatic Society.