Origin - The University of Birmingham - a chap rather accustomed to brightly coloured trousers.
Commonly used, though ill approved term (especially when uttered in the presence of a female) making reference to the genitalia of a female/general presence of a female.
Favoured most notably for its distinct onomatopoeic effect.
Can also be used with great effect to discombobulate a member of the female sex who is unaware of its definition. Pick your yat wisely, however, as you don't want to ask someone who knows the definition. This game is called 'Risk Gwatch'.