The symbol first originated in a Howard st night club (Baltimore, MD) where a nasty pig's gf requested aid with keeping prowlers at bay. Bf would stand behind her at the bar and release farts into the crowd to create more bar space. Often, the creepiest of stranger will greet you with the fart symbol, allerting you that they're a stinky foe long after beer goggles have kicked in.
TO PERFORM FART SYMBOL: Use American sign language to symbol "OK" with your right hand (Fingers apart, Thumb and index finger touching to form a circle).
"Oops, I didn't realize everybody here knew the fart symbol"
"Was she giving you the fart symbol?...Oh ok, that's your ex wife. Of course she doesn't know what it means...or does she?"