Cunt

Etymology:
This most energetic of cuss words probably comes from the ancient German ‘kunton’ meaning hollow place but its first use in English has links to the word ‘count’ or ‘counte’, which led oversensitive aristocrats to insist on being called Earl instead of count. Another suggested root is that of combe, a Gaelic word for valley. This, of course, raises some terrifying possibilities about the literal meaning of Anne Widdecombe’s name.

Essential use in cinema: Silence Of The Lambs
When Clarice Starling first goes to visit the charming and well groomed serial killer, Hannibal ‘The Cannibal’ Lecter, first she has to pass the Perspex cell of Farris Rotter the garrotter who shouts to her: “I can smell your cunt.” Which is a useful plot device allowing Hannibal to show how good his sense of smell is.