The origin of the symbol comes from the Catholic tradition that Peter the Apostle was crucified upside down,[1] as told by Origen of Alexandria. The tradition first appears in the "Martyrdom of Peter", a fragmented text found in, but possibly predating, the apocryphal Acts of Peter, which was written no later than 200 A.D. It is believed that Peter requested this form of crucifixion as he felt he was unworthy to be crucified in the same manner that Jesus died. As such, some Catholics use this cross as a symbol of humility and unworthiness in comparison to Jesus.