In 496 A.D. Pope Gelasius changed the name of the Lupercalia festival (Feb. 15th) to St. Valentine’s Day (Feb. 14th).
Lupercus was a name for the Greek god Pan, a satyr. His festival, celebrated annually on the anniversary of the founding of his temple, was called the Lupercalia. At that time, hungry wolves roamed outside Rome in the pastures. Lupercus watched over the shepherds and their flocks.
During the Lupercalia, the Romans sacrificed goats and dogs. Young men ran around with goat-skin thongs (called februa) and playfully lashed women in the streets. A februa lashing (a februatio) ensured fertility and easy child delivery.
In addition, the celebration featured a lottery. Names of girls were written on slips of paper and placed into a vase. Young men drew the names from the jar, and the two became partners for the festival, and sexual companions for the remaining year. Afterwards they would split, or if they wanted to marry they could do so.
After the Romans, the half-man/half-beast satyr increasingly became a great fear of men (especially in the Middle Ages). Men worried that these pagan satyrs would come from the forest and have sex with their daughters and wives. Similar fears are also seen in the story of Beowulf, a beast who comes from the woods to kill all the villagers in the mead hall. In the Middle Ages to the height of the witchcraft days, Satan was depicted more and more as a powerful satyr with his horns, tail, and hooves. Deep within the forest was the cradle of evil pageantry.

It comes as no surprise that the Lupercalia offended the young Roman Church. Stopping the historical Roman celebration would be a difficult task: the celebration was as embedded in Roman culture as Thanksgiving is to Americans.
Pope Gelasius, the most prolific writer in the early church, was the man to make it happen. The strategy of the early Church was to replace pagan festivals with Church-based ones (Easter instead of Spring Equinox, Christmas instead of Winter Solstice, all Saint’s Day instead of Halloween, etc). Pope Gelasius invented St. Valentine from a composite of men who were martyred due to chaste love.
A few hundred years ago, it would be unthinkable that the Church (then another cult) could have the power to do this. But the steady decline of the Roman empire and the legalization of the Church by Emperor Constantine I in the year 313 changed things.
In 494, Gelasius wrote a very influential letter on spiritual and temporal power that would rock the political landscape for a thousand years. The letter asserts that there are two key powers: royal power and the sacred authority of the priests (which was higher). Gelasius argued that the powers must work together in harmony, thus helping to integrate church and state. Eventually came the Age of Enlightenment. People like Martin Luther, Henry VIII, and the founding fathers of the United States helped weaken the church’s power over the state until eventually becoming separate.
The word February comes from the Latin Februarius (meaning, month of purification), which comes from februa (the thongs from the festival, meaning, undoing the fever), which was derived from the Latin febris, meaning fever.
May today be a Happy Lupercalia and a Happy February.
Pope Gelasius’s letter on spiritual and temporal power: http://www.fordham.edu/halsall/source/gelasius1.html