If you’re wondering where the dollar sign ($) came from, you’re in good company. No one really knows for sure, and several theories have emerged over the years. The most widely accepted explanation, according to the Bureau of Engraving and Printing, goes back to the Spanish peso, which was accepted as the basic unit of value in colonial America during the late 1700s.

Handwritten manuscripts dating to that time show that the peso—formally “peso de ocho reales” or “piece of eight” in America—was abbreviated PS. It’s believed that as time went on, the abbreviation was often written so that the S was on top of the P, producing an approximation of the $ symbol. The $ first appeared in print after 1800 and was widely used by the time the first U.S. paper dollar was issued in 1875.