There are about twenty modern nations whose currency is called the "dollar." The word apparently derives from "taler," which in turn comes from "Joachimsthal," the name of a place in Bohemia where the taler (a silver coin) was created—with the "-thal" part presumably meaning "valley." (The modern German spelling, by the way, has been changed to "tal," which explains the new spelling of the English word "Neandertal.") So as far as I can tell we use dollars today because certain coins were once minted in a valley.
A few months back I read a marvelous article (which I gather originally appeared in the New Yorker) on, among other things, the history of money. The author noted that at one point in human history cows were used as a medium of exchange, which is why the word "pecuniary" derives from pecu, meaning money or cattle. (To peculate, by the way, is to steal.) Hence, a syllogism:
Cows are the root of money.
Money is the root of all evil.
Therefore, cows are the root of all evil.
Whence we get the phrase "qui tollis pecu mundi," "he who takes away the cows of the world." In theological terms, such a taking-away is known as bovine intervention.
(And while I'm here, I might as well mention that "money" is from "Juno Monetas," at whose temple money was minted.)
Slang terms for money derive from some similarly unlikely places. I used to have trouble remembering whether a fin was a five-dollar bill and a sawbuck a ten, or vice versa, until I learned that "fin" (also "finnif") is from "finf," Yiddish for "five," and "sawbuck" refers to a kind of sawhorse with crossed wooden legs, forming an X, the Roman numeral for 10. A double sawbuck is thus a twenty-dollar bill. "Sawbuck" is sometimes abbreviated "saw," but not, of course "buck."
The 1920s and 1930s were a particularly rich time in terms of American slang terms for money, some of which are still in use today. Some terms presumably referred to money's use in purchasing food: bacon (as in "bring home"), bread, dough, and so on. (One term for counterfeit money was "sourdough.") Other terms referred to the green color of American bills: cabbage, lettuce, kale, folding green, long green. Yiddish was the source of some terms, such as "gelt"—though that particular one had been part of the English language since at least 1529, possibly by way of German and Dutch. There were other old terms for money: "rhino," for instance, of unknown origin, entered the language in 1670, two centuries before the word was used as a shortened form of "rhinoceros." I'm not sure, but I suspect that "jack" derives from "jackpot," originally referring to the large amounts of money you could win playing a jacks-or-better poker game. Some slang money terms I have no idea of the origin of: mazuma, moolah, oscar, pap, plaster, rivets, scratch, spondulicks. I wouldn't be surprised to learn that some monetary slang was invented by Damon Runyan or other writers of the time...
A dollar bill can be called a "rutabaga," for some reason—and in Rutabaga Tales, Carl Sandburg frequently uses the term "cash moneys." "Cash" referring to coins and paper money comes from French, Italian, and Latin, with roots referring to a money box—and is completely etymologically distinct from the Chinese and Indian coins called "cash," with roots in Portuguese, Tamil, Sanskrit, and Persian. Though both meanings of "cash" entered English in the last few years of the 16th century, so perhaps one influenced the other.
Other slang terms for a dollar include ace (which term derives from a word referring to a copper coin in Latin), bean (as in bean counter), boffo (presumably from Variety headlines' shortening of "box office" referring to money collected at theatres), bone, buck, bullet, case note, clam, coconut, fish (which in '20s slang could also refer to a convict), frogskin, lizard, peso, rock, scrip, simoleon, and yellowback. The heavy dollar coin was once known as an iron man, plug, sinker, or wagon wheel. And the old Spanish peso coin could be physically broken into eight pieces, each worth one real, an eighth of a peso; hence the coins were called "pieces of eight," and a 25-cent coin, a quarter dollar, is "two bits."
A $100 bill can be referred to simply as a "bill" ("He gave me five bills for the merchandise"), or as any of several variations on "century" (meaning 100), most commonly "C" or "C note." Another term is "yard," perhaps from the word's meaning of "a lot"—"He reeled off yards of data..."
A thousand dollars, of course, is a "grand," or a G for short.
In the USA, paper money is sometimes referred to as "dead presidents." This is a bit odd, since not all of the people pictured on money were presidents. Quick quiz: name the people shown on each denomination of American money currently in circulation, without looking.
- 1 cent (penny)
- 5 cents (nickel)
- 10 cents (dime)
- 25 cents (quarter)
- 50 cents
- $1 coin (two types; neither is currently minted or in wide circulation, but there are still some out there)
- $1 bill
- $5 bill
- $10 bill
- $20 bill
- $50 bill
- $100 bill
(The $500, $1000, $5000, and $10000 bills have not been printed since 1946.) Answers are on a separate page.
I found several of the above slang terms in the Justice, Inc. Campaign Book, a sourcebook (published by Hero Games) for pulp-fiction roleplaying games set in the 1920s and 1930s.