The Old Lady just bought half a yard of cable and there are plenty of bids for Bill and Ben.

Confused?

To most foreign exchange traders in London's City financial district that sentence would make perfect sense: The Bank of England just bought half a billion U.S. dollars worth of British pounds against the dollar and there's interest to buy the Japanese yen.

A mixture of Cockney rhyming slang, market banter and expressions picked up from horse racing bookmakers makes up the basis for a financial lingua franca that may sound like nonsense to most people, but has dominated the $4 trillion (2.60 trillion pounds) a day foreign exchange (FX) market for decades up until recently.

Most often used for currencies, countries and numbers, this financial market mumbo jumbo is starting to die out on the modern trading floors of international banks.

The growth of electronic dealing over computer screens rather than telephones or in person, a new generation of university-educated traders, and the introduction of the single European currency are all seen as reasons behind slang's demise.

These terms get batted around a little bit but not as much as they used to, said Graham Davidson, director of FX trading at National Australia Bank in London, who said dealing rooms in general are much quieter than they used to be.

FX is much more electronic. Lots of the slang came about through banter with the voice brokers, but that doesn't really work with machines. A lot of day-to-day chit chat has faded away, it's quite sad.

Some market players say the shift in the language of the dealing rooms also highlights a wider shift in the demographic of those doing the trading.

Many traders nowadays are recruited as university graduates with top marks from Oxford, Cambridge, Harvard and M.I.T., whereas 30 years ago aspiring youngsters with few, if any, academic qualifications often started as back office clerks and worked their way up to the trading floor.

Young London lads blessed with quick wits, common sense and ability to juggle numbers were often prized above those with academic laurels and went on to make fortunes as City traders.

They were the 'barrow boys' coming off the market stalls. It was more working class and with that came the language of the street, said one trader, who used to work alongside some dealers who also owned fruit and vegetable and flower stalls.

In the early days of dealing rooms it was the City institutions and especially the British banks where you heard it. Now dealing rooms might be a bit more international and slang is dying off a bit.

HALF A YARD OF CABLE

Some expressions have endured despite the changed dealing room environment. Yard, meaning billion comes from shortening the French word for billion, which is milliard.

Cable - one of the most-used slang terms - means the British pound/U.S. dollar currency pair and refers to the transatlantic telegraph cable that allowed prices to be transmitted between the London and New York Exchanges.

The Bank of England gained its title from its address, making it the Old Lady of Threadneedle Street, while the yen is nicknamed the Bill and Ben - after a pair of puppets from a 1950s British children's TV show - simply because it rhymes.

Country nicknames tend to conform to stereotypes, some less politically correct than others, while currencies were given nicknames to help distinguish them easily.

Some traders said if countries did give up the single European currency (euro) as a result of an on-going debt crisis in Europe, some slang might re-emerge.

We have talked about this a lot recently given the euro zone situation, and thought about what it would be like to go back to mark/Paris (deutschmark/French franc), a London-based trader said.

These days there are far fewer names to worry about - the euro is the euro. Whereas in years gone by you would have had to worry about what the Estonian currency was even called.

Short selection of City slang

NUMBERS:

A SPANIARD 1 From the Spanish name Juan

A PRICKLY 2 A prickly pear

A CARPET 3 UK prisoners used to be allowed carpet in their cells after 3 years

LADY GODIVA 5 Rhymes with fiver

AYRTON 10 Tenner rhymes with Ayrton Senna, the late racing car driver

A BULLY 50 From the 50-point bullseye on a dartboard

A MONKEY 500 The 500-Indian rupee note used to have a picture of a monkey on it

CURRENCIES:

THE LOONIE CANADIAN DOLLAR A waterfowl named the loon is depicted on Canada's one-dollar coin

THE KIWI NZ DOLLAR National bird of New Zealand

THE AUSSIE AUSTRALIAN DOLLAR

THE STOKKIE SWEDISH CROWN

THE NOKKIE NORWEGIAN CROWN

(Reporting by Nia Williams, editing by Paul Casciato)