It is claimed that in the Middle Ages, churches that were too poor to display the relics of martyred saints at Allhallowtide let parishioners dress up as saints instead. Some Christians continue to observe this custom at Halloween today. Lesley Bannatyne believes this could have been a Christianization of an earlier pagan custom. While souling, Christians would carry with them "lanterns made of hollowed-out turnips". It has been suggested that the carved jack-o'-lantern, a popular symbol of Halloween, originally represented the souls of the dead. On Halloween, in medieval Europe, fires served a dual purpose, being lit to guide returning souls to the homes of their families, as well as to deflect demons from haunting sincere Christian folk. Households in Austria, England and Ireland often had "candles burning in every room to guide the souls back to visit their earthly homes". These were known as "soul lights". Many Christians in mainland Europe, especially in France, believed "that once a year, on Hallowe'en, the dead of the churchyards rose for one wild, hideous carnival" known as the danse macabre, which has often been depicted in church decoration. Christopher Allmand and Rosamond McKitterick write in The New Cambridge Medieval History that "Christians were moved by the sight of the Infant Jesus playing on his mother's knee; their hearts were touched by the Pietà; and patron saints reassured them by their presence. But, all the while, the danse macabre urged them not to forget the end of all earthly things." This danse macabre was enacted at village pageants and at court masques, with people "dressing up as corpses from various strata of society", and may have been the origin of modern-day Halloween costume parties.
^ Not counting any other character in the mainstream Marvel Universe with that name. Only outside of the mainstream Spider-Man comics or in other media is there other Spider-Man villains (that isn't named Mac Gargan) that are antagonists of Spider-Man. Gargan is cited to be the fourth who is called that in the comic books but is the most iconic villain with that name.
I thought of something else that has to be considered in the rise of the superhero. As Joe Crawford notes, superhero comics and science fiction hit the mainstream together, sharing creators, distributers, and reading publics. Both deal with science and technology and their effects in society — in a characteristically (for the ’30s) optimistic manner. A man will come from a faraway planet and act as the world’s protector; another will use his wealth and brilliance to develop tools that will be used to fight crime in the streets. No problem — even those caused by science and technology — can not be solved by the application of science and technology. By the ’50s, with the advent of nuclear technology and the revelations of the Holocaust, this optimism is somewhat tempered — the new crop of superheros that emerged in the decades after WWII (Hulk, X-Men, Spiderman) were hunted, persecuted, plagued by superpowers they did not want, which they carried as a burden (and of course the resurgence of Batman and Superman put them into a similar mold).
The practice may have originated in a Celtic festival, held on 31 October–1 November, to mark the beginning of winter. It was called Samhain in Ireland, Scotland and the Isle of Man, and Calan Gaeaf in Wales, Cornwall and Brittany. The festival is believed to have pre-Christian roots. After the Christianization of Ireland in the 5th century, some of these customs may have been retained in the Christian observance of All Hallows' Eve in that region—which continued to be called Samhain/Calan Gaeaf—blending the traditions of their ancestors with Christian ones. It was seen as a liminal time, when the spirits or fairies (the Aos Sí), and the souls of the dead, could more easily come into our world. It was believed that the Aos Sí needed to be propitiated to ensure that the people and their livestock survived the winter.