[ “S” Goes to Jail ]
Like many people, I have used the dollar sign ($) without ever understanding precisely why an “S” with lines going through it represents the basic unit of American currency. I had heard initially that the sign comes from the expression “pieces of eight,” which is piratespeak for money. In that sense, the dollar sign was literally that — the “S” was actually the remaining chunks of the number 8, after having been divided by vertically cutting lines. But oh, if only it were that simple.[ all for you, lauren deny custard ]
There are quite a few other origin stories that don’t pan out either. One, proffered by the United States Mint, claims that the modern-day dollar sign evolved from a logo that combined the “U” and “S” in the institution’s name, though apparently not the “M.” Ayn Rand apparently endorses this explanation of the sign in Atlas Shrugged. According to the website of researcher Roy Davies, the tenth chapter of Rand's book is titled "The Sign of the Dollar," and in it Rand claims that "the dollar sign was the symbol not only of the currency, but also the nation, a free economy, and a free mind." Though this one would appear to make the most sense, most researchers have seemingly abandoned it as a possible explanation because the dollar sign predates the founding of the United States. (Suck on that, Ayn.) The U.S. Mint website doesn't even list it — or any — explanation in their FAQ section.
Another different history, offered by the U.S. Bureau of Printing and Engraving, claims that the symbol was born as a result of a union of the letters “P” and “S” — as in “peso” or “piastre” or “pieces of silver” or, again, “pieces of eight.” The "S" was apparently written in superscript next to the "P" in "old manuscripts," though these ancient documents aren't cited and God knows where they could be. (This website for the bureau mentions this origin on its FAQ page — scroll down to the bottom third of the page.) This explanation accounts for the fact that the dollar sign was in use to denote other forms of currency long before the United States officially adopted it in 1785, and as a result seems to be the most favored possibility. However, the one vertical bar of the "P" doesn't account for the two vertical bars of the sign itself. (Though I should note that the iMac keyboard I'm typing on now only shows the sign with one vertical bar.)
The Wikipedia site for the dollar sign has a neat little graphic depicting how either the P-S or U-S explanations might have come to be.
Other, less popular theories abound. One purports that the dollar sign derives from an abbreviation for "shilling" — a form a British currency popular around the same time the Britons were drawing slashes through things to indicate that an abbreviation was being used. The still-used symbol for the British pound — £ — also has a slash, albeit a horizontal one.
Another unpopular explanation links the sign to slavery — and the Spanish words esclavo and clavo, meaning "slave" and "nail," respectively. Davies writes that "the shackles worn by slaves could be locked by a nail which was passed through the rings or loops at the ends of the shackle and bent while it was still hot and malleable." In short, the bent loops of the shackle looked like an "S." Once locked, they looked like an "S" with a line through it.
"S" + clavo ("nail") = S-clavo, or esclavo, meaning "slave"
To me, this seems at best another folk etymology, though one that works nicely when you consider what a large part of worldwide economy slaves once composed.
There's even a proposed connection to the Portuguese cifrão, a remarkably similar-looking character that Brazilians use to mark the transition from dollars to cents, much as we use a decimal point. (Well, not dollars and cents, but escudos and centavos. But you get the idea.)
What the Wikipedia entry concludes with, however, is an even stranger origin story for this little guy — and in my opinion, the one that most smacks of the truth. Some theorists link the dollar sign to the Pillars of Hercules, the twinned outcroppings that mark the Strait of Gibraltar — the nautical gateway to the new world. The logo of the two pillars superimposed over images of earth's two hemispheres — Eurasia and this new America thing — appeared on popular Spanish coins after Columbus' expedition and remained there until well after the United States declared its independence from Britain. The two circles representing the then-known world devolved into an "S" and the pillars became twin vertical strikes.
This explanation accounts for the double strike as well as the signs worldwide popularity. After all, the United States isn't the only nation to employ the dollar sign. Argentina, Australia, Brazil, Chile and Cuba also use it. Finally, it makes for sense than the shilling theory, because it seems unlikely that the United States would employ an out-dated currency symbol once held by the then-hated Britain.
Somewhere in these, there's the truth, but I feel like someone with more time than I have will be the one to sort it out.