The Telegraph thinks that bunga bunga is either the punchline of a bawdy joke beloved of Berlusconi, or an 'erotic ritual' that the Libyan leader Colonel Gadaffi told the Italian PM about. The Irish Examiner says that a bunga-bunga is 'an after-dinner game for one naked man and a bevy of naked young women'.
There are only five words beginning 'bunga-' in the OED, but bunga bunga, nor indeed, bunga, isn't one of them. Perhaps there is something about the combination of letters 'bung' that makes this a good start for slang words. There are 52 entries in the OED that begin 'bung' but there are 72 entries in Jonathon Green's Dictionary of Slang that begin with these four letters. Several of the slang entries relate to the sense of bung as a slang word for 'anus' (not mentioned in the OED), several others to things to do with drinking, since a bung is a brewer or publican (the OED has 'bung-ho', a drinking toast) and yet others relate to the sense of bung meaning a bribe or a pickpocket (these senses are in the OED).
published on: The virtual linguist
Use it: Bunga-bunga for party. As in, "I went to Silvio Berlusconi's bunga-bunga in Milan last weekend. It was wild!"
Why: Because "party" is just so bland.
Source: Star Tribune