$ appears to have evolved circa 1775 in the United States from a common abbreviation for pesos, also known as piastres or pieces of eight, a P/raised-S ligature PS.[1] It was used in the US before the adoption of the dollar in 1785.[2]
The "computing" sense is the result of homophony between Englishcache and cash, dollars being a form of cash.
A substitute for the letter S, used as a symbol of money or perceived greed in business practices.
Micro$oft Window$
1971 February 26, “Motor City: March Special” (advertisement), in The Daily Herald-Tribune, volume 58, number 168 (in English), Grande Prairie: Bowes Publishers Limited, After Hours, page 2:
When used as a currency symbol, $ precedes the number it qualifies in English, despite being pronounced second. For example, "$1" is read as one dollar, not dollar one unlike the usage in languages such as French or German: "1 $", "2,50 $".
When used for the Portuguese escudo, $ is placed between the escudos and centavos, e.g. 2$50. The official symbol for the escudo is (with two bars), but that form is unified with the single-bar form in Unicode. A single-bar dollar sign is frequently employed in its place even for official purposes.
for the usage with explicitly two lines.
(with two bars), but that form is unified with the single-bar form in Unicode. A single-bar dollar sign is frequently employed in its place even for official purposes.
– cifrão