One of the most versatile slang available, it originated as an ancient tribal incantation of the East. It was used to call forth spirits of eccentricity and bewilderment, often inflicting the intended target with horror. Nowadays, it is mostly used in a flippant manner, telling people to cease talking in a most discourteous way.
"Hey! Let me tell you about the time I..."
(the most common response) "Well, fuck YOU too!"