The origin of the word
dollar comes from the coins that
Spanish emperor
Carlos I ordered to coin at the beginnings of the
XVIth century. They were of
silver, (read
Webster's wu for more precise information) and they had the same value as the
German thaler.
A century later, when the spanish thalers began to circulate in North America, they were called spanish dollars, as someone wrote "dollars" instead of "thalers".
When the U.S.A. became a nation, the dollar acquired the category of national currency. In those coins were engraved the Columns of Hercules, the symbol for the Spanish Empire, that ultimately were converted into the sign that epitomizes dollars and money everywhere:
$