http://www.designboom.com/contemporary/peace.htmlAccording to this site the peace sign was created in observation of nuclear dis-armorment. It was later abopted by the civil-rights movement as a sign of equallity and peace. The right wing saw this as a threat and tried to demonize it as a satanic symbol giving it a pseudo-history in satanic rituals dating back to the days of the Romans linking the peace sign to the "cross of Nero" that was later viewed as demonic. But like most symbols its really open to personal interpration. I was tought it was an inverted cross that was broken and was a christian symbol for peace symbolizing mercy towards Peter who betrayed his faith and was hung upside down as a sign of humilation. He believed he was unworthy to be hung like his master, Jesus. Later I realized that it looked just the Nordic Rune Tyr inverted. Tyr inverted could be taken to mean a variety of things among them peace. The circle being the symbol of endingness meaning the symbol itself means eternal peace. However the hippies in the anti-vietnam movement called it the chicken foot of America.
http://en.wikipedia.org/wiki/The_Hanged_ManAlso known as "the traitor" the hanged man symbolizes independance at one or another's expense, but this view varies depending on which deck you're going by. From what I was taught it was suppose to be Peter hanging upside down on a Roman style crusafix, or Tau cross. And it symbolized humility and the need for attonement, agian Peter was supposedly hung inverted on the Roman cross as a sign of being unworthy to die like Jesus. This connection between St. Peter may be the link between the peace sign and the hanged man. However, some believe that the hanged man is really the Norse God Odin depicted in the myth where he hangs from an Oak tree (I think it was oak) to gain enlightenment. As such, the card can be interpreted as attaining "enlightenment" or discovering some kind of revelation, a good card instead of negative. This Nordic link may also be the connection between the peace sign and the hanged man. Its really unknowable beyond speculation.
I think Peter more likely commited suicide than was hung from the cross. I think this because he would not have wanted to be captured by the Romans and humiliated but he also knew he could not use Jesus' teachings without being a total hypocrite. Regardless if my opinion is ture, I think Christians later adopted the Norse myth of Odin, much like they did with other pagan stories, to Christianize the heathens of old.
Really though the Da Vinci code shouldn't be taken as anything more than a fancy peace of historical fiction. Yes I think the ideas presented by the book and movie are interesting but nothing more than entertaining. Much of what Dan Brown preported to be historical fact is really not true and his "facts" are a gimmick to draw readers into his novel. Genius yes but only entertaining.