1550s, from Low German daler, from German taler (1530s, later thaler), abbreviation of Joachimstaler, literally "(gulden) of Joachimstal," coin minted 1519 from silver from mine opened 1516 near Joachimstal, town in Erzgebirge Mountains in northwest Bohemia. German Tal is cognate with English dale.
The thaler was a large silver coin of varying value in the German states (and a unit of the German monetary union of 1857-73 equal to three marks); it also served as a currency unit in Denmark and Sweden. English colonists in America used the word in reference to Spanish pieces of eight. Continental Congress July 6, 1785, adopted dollar when it set up U.S. currency, on suggestion of Gouverneur Morris and Thomas Jefferson, because the term was widely known but not British. But none were circulated until 1794.
When William M. Evarts was Secretary of State he accompanied Lord Coleridge on an excursion to Mount Vernon. Coleridge remarked that he had heard it said that Washington, standing on the lawn, could throw a dollar clear across the Potomac. Mr. Evarts explained that a dollar would go further in those days than now. [Walsh]The dollar sign ($) is said to derive from the image of the Pillars of Hercules, stamped with a scroll, on the Spanish piece of eight. Phrase dollars to doughnuts attested from 1890; dollar diplomacy is from 1910.
bet one's bottom dollar, hot as a three-dollar pistol, phony as a three-dollar bill, top dollar
originally, a silver coin that circulated in many European countries; in modern times, the name of the standard monetary unit in the United States, Canada, Australia, New Zealand, and other countries. The Spanish peso, or piece of eight, which circulated in the Spanish and English colonies in America, was known as a dollar by the English-speaking peoples. Familiarity with this coin resulted in the official designation of the United States monetary unit as the dollar in 1792. Canada adopted the dollar and monetary decimal system in 1858; Australia in 1966; and New Zealand in 1967.