Historical Origin of the Celebration
A popular explanation of the link between Saint Valentine and the Holiday says that at the time of the Roman "Lupercalia" Festival marriage was a common tradition, but when Claudius became Emperor he changed all of that. He outlawed all marriages because he was afraid that men would refuse their duty to fight because they would not want to leave their wives behind. Young couples still fell in love though and still wished to marry and they took these desires to the Catholic Bishop Valentine who, understanding love, began to secretly marry couples. When Claudius found out, he arrested Valentine and sentenced him to death. While waiting in prison, Valentine began exchanging letters with the prisoner's daughter and soon had fallen in love with her. The day he was to be beheaded, he wrote her one last note and signed it: "From Your Valentine".
In 496 A.D. Christianity had taken over Rome and Pope Gelasius outlawed the pagan Lupercian Festival. Knowing it’s popularity, he looked to replace it with something more "appropriate" and set aside a day in February to honor the martyr St. Valentine. Even though in 1969 the church removed St. Valentines Day from it’s calendar of "official" holidays, it is still widely celebrated today. And although Valentine's Day has become quite commercial, it still contains an important aspect shared by all of the best holidays – time spent thinking of and being with the one you love.
Source: Wikipedia
