Bunga bunga is a phrase of uncertain meaning that dates from 1910, and a name for an area of Australia dating from 1852. By 2010 the phrase had gained popularity in Italy and the international press to refer to former Italian Prime Minister Silvio Berlusconi's sex parties, which caused a major political scandal in Italy.
In 1910 Horace de Vere Cole, Virginia Woolf, her brother Adrian Stephen and a small group of friends, pretended to be the Prince of Abyssinia and his entourage. They obtained permission to visit one of the world's most powerful warships HMS Dreadnought in Weymouth, Dorset, in what became known as the Dreadnought hoax. Each time the Commander showed them a marvel of the ship, they murmured the phrase bunga, bunga! which then became a popular catchphrase of the time.
A 1950 Bugs Bunny short "Bushy Hare" used the phrase "Unga Bunga Bunga" in a nonsensical exchange between Bugs Bunny and a character who represented an Australian Aborigine and who was referred to as "Nature Boy". 
Resurgence in Italy
A century later, the term bunga bunga became popular again as a joke on the internet. This joke was then narrated by Italian Prime Minister Silvio Berlusconi at his dinner parties (in a version which featured, as prisoners, former ministers from the center-left opposition party led by Romano Prodi).
This expression was then frequently quoted by the Italian and international press during the 2011 investigation surrounding Silvio Berlusconi's underage prostitution charges, acquiring a quite different meaning as "an orgy involving a powerful leader"; as such, it was allegedly taught to Silvio Berlusconi by Muammar al-Gaddafi, who was also the unwitting originator of the phrase Zenga Zenga.
In Italy, the term "has become an instant, supposedly hilarious, household expression".
Recent explanations disagree on its meaning, or perhaps illustrate the range of its reference. It "is said to be a sort of underwater orgy where nude young women allegedly encircled the nude host and/or his friends in his swimming pool", "an African-style ritual" performed for male spectators by "20 naked young women", or erotic entertainment hosted by a rich host involving pole dancing and competitive striptease by skimpy-costumed "women in nurses' outfits and police uniforms" — but topless women, the prize being prostitution for the host.
In 2011, the faux-French, American band Nous Non Plus released a song entitled "Bunga Bunga". The cover of the single featured a picture of Silvio Berlusconi. The song lyrics list famous cities around the world (in French) while the video is a black and white showreel of semi-nude dancing women.
In 2012, the term was used in the British motoring show Top Gear in Season 18, Episode 1. It was used to describe The Stig's Italian cousin, who emerged from a motor-home dressed in a suit, followed by three glamorous girls, to set a lap time in a Ferrari 458 Italia at the Imola circuit.
In 2013, the American band Cherry Poppin' Daddies used the term several times in the lyrics for their song "The Babooch", a satire of "one-percenter" lifestyles. The song's music video features clips of Berlusconi alongside other billionaire figures.
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- The Dreadnought Hoax", Museum of Hoaxes. Retrieved 24 January 2011. This anonymous article cites Adrian Stephen, The Dreadnought Hoax (Hogarth Press, 1983).
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- IMDB. "Bushy Hare" http://www.imdb.com/title/tt0042291/
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- Tom Kington, "Silvio Berlusconi reels as 'Ilda the Red' lands the first blow in sex offences case", The Observer, 16 January 2011. Retrieved 18 January 2011.
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- Thane Burnett, "Academic charts expanding universe of slang", Toronto Sun, 20 January 2011. Retrieved 23 January 2011.
- iTunes Music Store. "Bunga Bunga - Single" https://itunes.apple.com/gb/album/bunga-bunga-single/id462223591/
- Come Into Land. "NOUS NON PLUS – “BUNGA BUNGA"" http://comeintoland.com/2013/05/22/nous-non-plus-bunga-bunga/
- Mansfield, Brian (July 2, 2013). "Video premiere: Cherry Poppin' Daddies' 'The Babooch'". USA Today.