Cockney rhyming slang is a living body of language. It must be, because I know a young man who coined the phrase “knife and fork” (orc) and I myself coined “Caerphilly” (willy).  Since both terms are in use by more than one person, only a miserable twit would deny they have entered the English language.
Not only Londoners but also many other British people too are familiar with the term “cobblers”, nowadays most often used to communicate that an assertion or story is rubbish, nonsense or bullshit. (“That’s a load of old cobblers“.)
Far fewer are aware that “cobblers” is short for “cobblers’ awls” , the Cockney rhyming slang for “balls”, itself a much-used metaphor for testicles.  Use of the term “cobblers” in direct reference to a male’s secondary sexual organs (e.g. “a kick in the cobblers” or “mind out for your cobblers“) is today uncommon. I even encountered somebody who learnedly advised that the term did carry such a meaning, yes, because he’d heard it used that way in an episode of the BBC TV series Steptoe and Son.  Clearly he hadn’t stayed in my house.
Another Cockney rhyming term for balls is “orchestra stalls“. Now very rare, it was used a fair bit by my uncle, whose father, my grandfather, was a Cockney by most standards even if he was born in Battersea. 
A third phrase for testicles is “town halls“. I’m not sure this originates in London, given that London isn’t the only city where denizens have developed rhyming slang. Rhyming forms have also been coined in Glasgow, including two rather scary references to commercial brands: “Mars bar” (a verb meaning to “scar” someone) and “radio rental” (an adjective meaning “mental”) . The only person whom I have heard refer to a dog licking its “town halls” is Mike Harding, the Mancunian socialist and comedian who for all I know may have invented the term. 
When an English posh boy gets prime-time publicity for climbing a mountain, and then some fawning interviewer asks him why on earth he does it, his reply will never be cut from the tape if he explains, in truly adventurous style (but how boringly unoriginal can you get?), “because they’re there“.  This is very similar to the common explanation for why a dog licks its balls: “because it can“.
The idea that a dog licks its balls because it can” is well enough known to be used in a more layered witticism, which I heartily recommend to you.
You know the kind of idiot who thinks he’s sophisticated (and it’s always a he) to quip “Does the bear shit in the woods?” or “Is the Pope Catholic?” when he is asked a question to which he believes the answer is obvious? Perhaps he also enjoys asking “How long is a piece of string?“, to which my favourite response is “Pieces of string can be all different lengths“. But sadly the kind of dimwit who asks “How long is a piece of string?” is usually too up himself to get the point.
Well when somebody asks you “Why did that lawyer charge me more than he said he would?“, “Why do estate agents tell lies all the time?” , or “Why will it take the company 10 working days to return my overpayment?” here’s your answer:
“Why does a dog lick its town halls?“
1) Whether a term can be coined as a loanword without having first been used in the supposed original language is an interesting question. Think of gimmick, which sounds Yiddish but hasn’t been traced to that language. Unfortunately since Cockney rhyming slang isn’t a language, this isn’t directly relevant here.
2) An awl is a pointed tool used for making holes in wood or leather.
3) Other terms include “nuts”, and in Russia, the word for “eggs” (яйца – yaitsa).
4) Steptoe and Son was a comedy series broadcast by the BBC, the British state’s broadcasting outfit, in 1962-65 and 1970-74. It has as its main characters an aging Cockney widower and his adult son who run a rag-and-bone business. The son wants to do better; his father couldn’t give a toss. They care deeply for each other. Films based on the series came out in 1972 and 1973. The second film contains marketing for affordably-priced holidays in fascist Spain, at a time when they were being heavily marketed to the lower orders in Britain and when many British coastal resorts, from Margate to Ayr, were being left to go to pot. I think a film based on the series On the Buses contains the same kind of propaganda. Today it would probably mention Facebook every few minutes. Newspapers now contain more references to Facebook and Twitter than they ever did in the past to other big brands, even to a one-time global monopoly such as IBM or a giant such as Coca-Cola or General Motors.
5) We will be writing more about the inner London area of Battersea some time. It has a fascinating history that isn’t talked about half as much as the history of the East End, where so many trendy artists now hang out.
6) Lest you imagine this term sounds rather cuddly, be aware that a person who’s called “mental” in Glasgow is at little risk of being considered calm and sane anywhere else.
7) Mike Harding said that if he met Margaret Thatcher the only things he’d have to say to her would be about sex and travel – in other words he’d tell her to “fuck off“. You know damned well that in the event he was ever offered a royalist medal by the posh boys, he would tell them to shove it.
8) Said intrepid mountaineer is unlikely to mention that a third prerequisite of his voyage in addition to the existence of the topographical feature and the presence of his desire to climb it was that he could afford the equipment – or that he had the connections to be able to persuade sponsors to give it to him – whereas most people do not find themselves in such a fortunate position. The message that’s conveyed is of course that the difference between him and a working class lad who’d love to climb Himalayan mountains if only he had the opportunity is that the posh boy has a better character. It’s as if inherited wealth has nothing to do with it.
9) An estate agent is known in some places as a realtor or real estate broker, and in Ireland as an auctioneer.