No, this is not a large human settlement in the state of Tennessee, but rather a human trait that instills an individual to not give up. This determination becomes deadly if a person is your enemy and is dead set on taking you out, just like a Navy Seal or, worse yet, Chuck Norris. What chemistry is oozing through their brains that drives them to these superman proportions is unknown. Militaries from many governments have been seeking this formula for centuries, to insert into their soldiers and turn them into robust, raving robots. The US military experimented with LSD and got mixed results, the worst being the soldier attacked everyone, including his own officers. So back to the chemistry labs they went and tried cocaine. Control was a little more favorable, but paranoia from sleep deprivation pretty much nixed this avenue. Ethyl alcohol was given a chance, but dosages varied so much, the results were unpredictable, and this path was terminated. Comic strips had fictitious characters that had great tenacity in reaching their goals and, thus, became known as superheroes. These morphed into movies with tremendous special effects that wowed their audiences and set new box office records that cascaded cash into the company coffers. Exponentially nice. These superheroes began surfacing in American comic books in the late 1930’s, at the end of the Great Depression. The artists were paid to promote their characters as a marketing tool for cigarette companies. Superman was seen flying around Metropolis, fighting crime with a lit cancer stick hanging out of his mouth. Batman cleaned up the criminals of Gotham City while puffing on a fag. The Flash would whip to the store to supply all the superheroes with cartons of crime fighting lung rockets. The tenacity of this smoking elite gang prompted its readers to light up. There was no effort by any medical institution to get these misguided souls to stop smoking. After all, no one likes a quitter.