According to the New Catholic Encyclopedia article by E.Day, February 14th commemorates two martyrs named Valentine, one martyred in Rome and the other in the city of Terni. That there were two Valentines is still disputed but, according to the text, “the late medieval custom of sending love notes on Saint Valentine’s Day stems probably from the belief that it marked the mating season of birds.” You could also check out the Wikipedia article about Saint Valentine or Valentine’s Day for more informa