Derived from an ancient story of French decent. The French bastards were searching for the lost city of Heracleum. Egypt was desperately trying to locate their city of gold which had become submerged under water some 2300 years ago (rough estimate). Egypt was well on their way to locating the city when they discovered the technique of tying pyramid rocks to their asses to pull them down significantly faster. French also had a good technique, they would take live lobsters and shove them up their ass so the tail would stick out and flap around acting as a propeller. There is no clear evidence as to who discovered this city, if it was discovered at all. Some say it was discovered but kept hidden. It is fairly evident that the Egyptians technique did not work considering 45 of the 46 test dummies never surfaced again. The only person to surface only did so because when he got to the bottom he allegedly shoved a lobster up his ass to propel him to the top. When he surfaced he had one quote before he died of unknown causes. He said "What the fuck were we thinking?!" in some strange tongue (some believe this tongue to be Egyptian, due to the fact that Egyptian was his nationality).
A great dispute started over who created the "'Tail' of the Lobster-Ass" due to the death of the Egyptian. This caused a great battle involving the Egyptions taking two lobsters to the sleeping French shoving one WAAYYYYY up his asshole and clamping one to the frenulum of his penis. Some believe this is the beginning of era where the French become large salty assholes, due to the large lobster, fresh out of the the salt water, being shoved up their ass. No correlation was made the lobster clamping onto their penal skin.
Now-a-days this is a common prank done among teenagers but the teenagers need to be really really fucking hammered to the point where the victim wont remember how he got the lobster in his ass. He wakes up questioning himself. This prank is extra funny because it often convinces the teenager that he is gay with a lobster fetish.
Never used in everyday dialog except to say, "What fucking moron wrote the definition of The 'Tail' Of Lobster-Ass?"