it started as a genuine typo for 'innit' but it means so much more now. It's when 2 people really know what the other is saying, and are fully in tune and concur.
A ning-nong, frequently abbreviated to nong, is someone who has done something stupid or clumsy and has caused a nuisance to others. Although it is can be an insult, it is often used affectionately, especially by Australians.
"Ah Charlie, you're such a ning-nong!" (in reply to a deliberately weak joke.)
Why did you go and invite that ning-nong to our barbecue? He's embarrassing all our guests!
"Stop being such a ning-nong, will you? You're upsetting your sister!
A magicall place invented by Spike Milligan, somewhere past the Black Stump, but not quite as far as Timbuktu. Famously popularized by the popular adult television programme Play School.
On the Ning Nang Nong Where the Cows smoke Bong, and the monkeys all throw poo, There's a Nong Nang Ning Where the fat man sings, and the tea pots sing along too. On the Nong Ning Nang all the mice get banged, and you just can't catch 'em when they do, so its Ning Nang Nong, Cows smoke Bong! Nong Nang Ning, the fat man sings, Nong Ning Nang, The mice get banged, What a noisy place to belong, is the Ning Nang Ning Nang Nong!!!