Slang terms for money often derive from the appearance and features of banknotes or coins, their values, historical associations or the units of currency concerned. Within a language community, some of the slang terms vary in social, ethnic, economic, and geographic strata but others have become the dominant way of referring to the currency and are regarded as mainstream, acceptable language (for example, "buck" for a dollar or similar currency in various nations including Australia, Canada, New Zealand, South Africa, Nigeria and the United States).
Argentina
In Argentina, among the years and despite many devaluation milestones, the lunfardo managed to persist in time some special nicknames to certain amount of money, not because color or type of the bill but to different meanings and uses.
Senior people above 65 now (previous to baby-boomer generation) used to call "guita" to the coins of low denomination of cents ('centavos'), like 2, 5 or 10 cent coins. So "10 guita" meant 10 cents of peso. Today the cents are still legal but non-existent. The word "guita" in lunfardo is synonym for "money".
During the short period of the "Austral" which replaced the traditional "Peso" monetary bill, after the dictatorship of 1976 (between 1983 and 1990) and in the recent years after year 2.000, people used to call "palo" (stick) to the "million" of australes or pesos, so "2 palos" refers to 2 million pesos.
For the last 20 years or more, after year 1997 at least, and during the government of president Menem, as probably the hiatus of the pre-devaluation era before year 2000, and even today people got used to call "luca" to thousands of pesos, so "5 lucas" it means 5 thousand pesos. Lucas, is a typical masculine name among the X Generation in Argentina.
Then another nickname for the singular peso is "mango", but nobody would call 35.000 "mangos" when they can say 35 "lucas". Also nobody would say 1.000 "lucas" when they can simply say 1 "palo" (1 million pesos)
Australia
Current denominations
The five-cent coin is sometimes referred to as "shrapnel" as the smallest remaining coin in value and physical size. This nickname was inherited from one- and two-cent coins when they were abolished in 1996. Similarly related (as is also used in the United Kingdom for pounds), "fivers" and "tenners" are relatively common expressions for five and ten dollars, respectively. "Beer tokens" can relate to any denomination or combination of. This is also in keeping with the reverse, in which "bottle tops" can be used as an expression of holding, offering, or having a low amount of money.
A twenty-dollar note is called a "lobster" or redback because of its red colour.
A fifty-dollar note is also known colloquially as a "pineapple" or the "Big Pineapple" because of its yellow colour.
The $100 note is currently green and is known colloquially as a “watermelon” not an avocado this is from TikTok, but between 1984 and 1996 it was grey, and was called a grey nurse (a type of shark).
In a Simpsons episode set in Australia, one character used the term "dollarydoos" which was later the subject of a failed petition to formally change the name of the Australian dollar.
Former denominations
Pre-decimal currency in Australia had a variety of slang terms for its various denominations. The Australian threepence was referred to as a "trey" or a "trey bit", a name probably derived from old French meaning three. The sixpence was often referred to as a "zack", which was an Australian and New Zealander term referring to a coin of small denomination, probably derived from Zecchino. The term was also used to refer to short prison term such as six months. An Australian shilling, like its British counterpart, was commonly referred to as a "bob", and the florin was consequently known as "two bob". Similarly, one Australian pound was colloquially described as a "quid", "fiddly", or "saucepan", the latter as rhyming slang for "saucepan lid/quid". The five-pound note could be referred to as a "fiver", or its derivatives, "deep sea diver" and "sky diver".
A number of post-decimal denominations which have since been discontinued had their own nicknames. The two-dollar note was known as the "sick sheep" in reference to its green colour and the merino ram that it showed. The paper (first and second series) hundred-dollar note was nicknamed the "grey ghost", "grey nurse", or the "Bradman" in recognition of its proximity to the 99.94 batting average of cricketer Donald Bradman.
Canada
In Canada, the one-dollar coin is known as the loonie. This is because it bears an image of the common loon, a bird.