It's a peso sign. The English word for the Spanish "peso" at the time was "dollar", and the US dollar was initially defined to be equal to the Spanish "dollar". The US dollar, which was a coin, had the same value as the Spanish peso because it consisted of the same weight (in Spanish, "peso") of silver. So the US used the peso sign for its dollars. Unicode calls it a "dollar sign" because that's what ASCII calls it, and that's because ASCII is from the US. But it's really a peso sign.
https://en.wikipedia.org/wiki/Peso
> In most countries of the Americas, the symbol commonly known as dollar sign, "$", was originally used as an abbreviation of "pesos" and later adopted by the dollar. The dollar itself actually originated from the peso or Spanish dollar in the late 18th century.
https://en.wikipedia.org/wiki/Dollar_sign#History
> The symbol appears in business correspondence in the 1770s from Spanish America, the early independent U.S., British America and Britain, referring to the Spanish American peso,[1][2] also known as "Spanish dollar" or "piece of eight" in British America. Those coins provided the model for the currency that the United States adopted in 1792, and for the larger coins of the new Spanish American republics, such as the Mexican peso, Argentine peso, Peruvian real, and Bolivian sol coins.
https://en.wikipedia.org/wiki/Spanish_dollar
> Most theories trace the origin of the "$" symbol, which originally had two vertical bars, to the pillars of Hercules wrapped in ribbons that appear on the reverse side of the Spanish dollar.[6] ¶ The term peso was used in Spanish to refer to this denomination, (...)