An argument could be made to call it a Cross of Humility. Even though the “official” name for this cross is, in fact, the Cross of St. Peter, it came to be called so after St. Peter, who had been condemned to be executed by crucifixion, asked that he be crucified upside down because he thought he was unworthy of being killed in the same way as Jesus Christ. I can see how it might be also called a Cross of Humility…