apparently the $ sign has its origins in the spanish Peso, where the p and s were gradually being merged together in abbreviations.
futhermore the US Dollar itself stems from the Spanish Dollar:
"The U.S. dollar was directly based on the Spanish Milled Dollar when, in the Coinage Act of 1792, the first Mint Act, its value was fixed [..] as being "of the value of a Spanish milled dollar as the same is now current
futhermore the US Dollar itself stems from the Spanish Dollar:
"The U.S. dollar was directly based on the Spanish Milled Dollar when, in the Coinage Act of 1792, the first Mint Act, its value was fixed [..] as being "of the value of a Spanish milled dollar as the same is now current