How St. Valentine became the patron saint of lovers remains a mystery, but one theory is that the Church used the day in an attempt to Christianize the old Roman Lupercalia, a pagan festival that entailed putting girls’ names in a box and letting the boys draw them out. The Church substituted saints’ names for girls’ names, but, by the 16th century, it was once again girls’ names that ended up in the box. Eventually, the custom of sending anonymous cards or messages to those one admired became the accepted way of celebrating St. Valentine’s Day. Discuss
Source: The Free Dictionary