It stands for Fragile Oblong Gangplank, in actuality. The term originated on the decks of Edward Teach's (Blackbeard's) ship: the Queen Anne's Revenge. Apparently, the ship was docked at Tortuga for months on end, the pirates spending their ill-gotten gold on cheap rum and prostitutes. Captain Benjamin Hornigold, pirate, turned privateer, turned pirate hunter sailed into Tortuga and stumbled upon Blackbeard's moored vessel totally bereft of crew and captain, and decided to lead his hardened soldiers aboard to set a trap for the crew when they returned.
Unfortunately, the gangplank they used to board the vessel was rather dilapidated, as well as being perched rather precipitously on the shore (no doubt the handiwork of a sloppy, rum-riddled crew). Captain Benjamin, sword drawn and cold grin in place, hurriedly approached the ship guiding his troops eagerly. Perhaps he was too hasty in his approach, or maybe the gangplank was ready to flip no matter the care used... but Captain Benjamin found himself floating next to the hull of the ship in the freezing night time ocean, soggy crew and broken gangplank along for the dip. He screamed 'Fragile Oblong Gangplank!' at the top of his voice, alerting the nearby pirate sentries (who had been napping in a rum-soaked stupor).
Before they could recover, Captain Benjamin's crew were surrounded and taken prisoner by the dirty, drunken pirates. Over time, after prolonged torture and imprisonment, the pirate hunters were conscripted to work the decks of the Queen Anne's Revenge. Blackbeard exploited their expert fighting abilities by using the soldiers as the first wave of attackers on unsuspecting traders. They quickly earned a reputation as some of the toughest pirate fighters around.
Unfortunately, the noble Captain Benjamin was not content serving under Blackbeard, and one botched escape attempt later, he found himself being forced to walk the plank. Realizing escape was not possible, Captain Benjamin Hornigold decided to face his fate like a man, and show no fear. He took a steady step forward, and cried out in shock as the plank gave way before him. He took a second surprise plunge into the salty sea, and he hit the water in chorus to 'Fragile Oblong Gangplank' and cackling laughter.
The established members adopted the title of FOG, due to their excellent ability at fighting dodgy traders and their cranky, swashbuckling nature. Also, it is a reminder to watch your step when you are going somewhere new, because you never know when you are going to encounter a Fragile Oblong Gangpank and plunge head first into the murky waters of the 'banned'
