The origin of the skull and crossbones symbol is an unsolved mystery that leads historians back over nearly two thousand years. It is said that the symbol first appeared well before even the Middle Ages. Members of the Christian religion created one of the first uses for the symbol in the late times of the Roman Empire and into the Middle Ages. They believed that the skull and crossbones symbol was to be used as a funerary symbol. It has been found in various Christian catacombs around Italy, some of which date back as far as the second century. During the same early period, the skull and crossbones was also considered to represent 'memento mori', a Latin term used in Rome that can mean, 'Remember death'. This term is supposed to warn those who think they are immortal that they are in fact mortal along with every other human and that there will be a time when they die. A trend with the symbol became clear, it generally depicted death, either in a respectful funeral symbol, or a warning. This trend continued into the Middle Ages as many people, Christian or not, began to have it carved into their tombstones.

However, as the Middle Ages progressed into the 1400s, the use of the skull and crossbones began to diminish until it was almost non-existent. The symbol was essentially unused during the following century, until it was adopted to be the symbol of some of the most feared people in the world, pirates. Originally, pirates used simply a red flag on the top of their ships’ mast. The red symbolized bloodshed and the fact that they gave no quarter (show no mercy). However, many pirates soon changed their flags from red to black and began to illustrate and weave the skull and crossbones into them. They did this because the pirates wanted to be feared, and black has always been the principle symbol for death, which is what many fear the most. They situated the skull and crossbones on their flags because the symbol stands for death as well. It was also an intimidating sign to other people, and distinguished the pirates from everyone else because there was no other symbol quite like it. In Miranda Bruce-Mitford’s book, The Illustrated Book of Signs & Symbols, she says, 'the skull-and-crossbones emblem were adopted by pirates as a sinister warning of their evil intentions. The emblem filled sailors with dread, and signaled death to all who saw it.' At that time, a symbol that once represented a respectful funeral had turned into one that struck fear into all who saw it. The symbol had come to represent death by destruction, instead of its original purpose of a peaceful death for the Christians. However, the symbol’s prominence once again began to disappear, as by the early stage of the 1700s, the golden age of piracy came to an end.

The skull and crossbones did not appear as a major recognized symbol again for nearly another two centuries, when members of the prestigious Yale University formed a secret society called 'Skull and Bones.' The Society has been a part of the university since 1832, and is still one of the most illustrious societies to be invited into. This society embraced the skull and crossbones symbol, not to represent death, but to represent the mystery that is their society. They have continued to use the symbol as the society reigns as strong as ever.

Soon after the society was created, the symbol took on another use as well. In 1829, a New York State Law required that all containers of poisonous substances be labeled. In 1850, the skull and crossbones was chosen to be the picture illustrated on those labels. The skull and crossbones image has lasted on poisonous materials labels up until now. It now, in a sense, once again represents death and draws undivided attention to those who see it, however, this time around, it is meant to protect, instead of endanger.