It is a gesture meant to indicate a sexual act, wherein the first and second fingers enter a vagina, while the errant pinky plunges into the anus; hence the "shock".
"Man last night I was going down on my girl and instead of doing some muff diving I gave her the SHOCKER!"
"The what?!"
"You know TWON IN THE PINK ONE IN THE STINK!!!"
"The what?!"
"You know TWON IN THE PINK ONE IN THE STINK!!!"
by Kenneth Allen Bryant II "AL" October 24, 2004
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