Hi, I’m Craig. I have a tattoo of a dollar sign on my knee so I can call it my “Money Knee”, and this is Mental Floss on Youtube!

Today I’m gonna answer Varun Dabral’s big question: Where does the dollar sign come from? I have to start by saying that unfortunately we don’t know where the dollar sign came from, but today I am gonna tell you the most popular and widely accepted theory. Let’s get started. Cha-ching!

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This theory comes from mathematician Florian Cajori who published his findings in the 1928 book, A History of Mathematical Notations, which I’m sure is some great light reading. In order to properly explain Cajori’s research, I’m also going to give you a little history of where the U.S. dollar came from.

As you probably know, the U.S. Constitution gave Congress the right to coin money. So in the late 1700s the U.S. began coining its own dollars based on the Spanish dollar. And they were coins; paper dollars didn’t exist until 1861. Because instead of making it rain, they had to make it hail, and that was dangerous. The Spanish dollar, also known as the Peso, had already been around since the mid 1500s. Fun fact: “Peso” is Spanish for “weight”, but the U.S. colonists got their word “dollar” from the European currency called “taler”.  

Anyway, Spanish-Americans began abbreviating “peso” in different ways in the 16^th Century. One popular abbreviation, P.S., evolved by the letters P and S getting kind of squished together into a new symbol. PS! PS! The symbol changed to the dollar sign that we know today. According to Cajori, that’s probably just because it’s easier to write it without the extra loop. So in addition to borrowing the Spanish dollar, people from the U.S. probably borrowed the abbreviation from the Spanish-Americans. Or to abbreviate: The Spanicans.

So when did all of this happen? Well Cajori had a pretty good idea thanks to the diary of a member of the New York Provincial Assembly in the 1770s. In the diary, from June 10^th 1776 through August 20^th, the word “dollar” is spelled out. But on August 21^st 1776 he uses the dollar symbol for the first time. Of course it’s not like everyone started using the dollar sign on August 21^st 1776, but that shows a good time frame for when the symbol was becoming more common. And by the 1800s, the dollar sign was pretty standard. I…I even use it today.

It's a good theory of where the dollar sign originated, but there are plenty more like it. Some believe that the sign came from the letters U and S, as in United States. That makes sense considering the dollar sign looks like a U on top of an S, minus the bottom of the U. Does that make sense? I don’t know…  Some people believe that it’s a U and an S, but that it stands for “Unit of Silver” rather than “United States”. Another theory is that the sign comes from a slash through an eight, because “Peso” is known as “Peso de ocho” or “piece of eight”. All of these theories are valid, and so is my theory that it was designed based on a snake going down a fireman’s pole.

If you have a big question that you’d like answered, leave it below in the comments. Thanks for watching Mental Floss on Youtube. Looking forward to spending time with you next week!

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