The association of middle of February with love and fertility goes back to ancient times. While ancient Athenians celebrated it as the month of Gamelion to celebrate the marriage of Greek Gods - Zeus and Hera, ancient Romans celebrated the Feast of Lupercalia to honor the Roman Gods of fertility - Lupercus and Faunus.
Ancient Athens celebrated the period between mid January and mid February as the month of Gamelion. They dedicated the festival month to the sacred marriage of Zeus and Hera. In Greek mythology Zeus was the supreme ruler of the ancient Greek Gods while Hera was the Goddess of women, marriage and childbirth.
Ancient Romans celebrated the ides of February as the festival of Lupercalia to secure fertility and keep out evil. The Feast of Lupercalia was dedicated to the Roman Gods of Agriculture, Lupercus and Faunus along with Romulus and Remus - the legendary founders of Rome. A precursor of this festival was celebrated on February 14. The day was observed as a holiday in honor of Juno - the Queen of Roman Gods and Goddesses and also regarded as the Goddess of Women and Marriage.
During the February Fertility Festival of Lupercus, members of Lupercali an order of the Roman priests would gather in a sacred cave where Romulus and Remus are said to have been nurtured by she-wolf or lupa. To mark the beginning of the festival, priests would sacrifice a goat for fertility and a dog for purification. Young boys used to slice the goats hide into strips and dipped them in sacrificial blood. Later, boys clad in animal skin would run about the streets of Rome holding pieces of goatskin above their head and gently slapping women and fields with the animal hide. Womenfolk gladly received the slap, as they believed that touch of the goatskin would render them fruitful and bring easy childbirth. Because the youths impersonated male goats (the embodiment of sexuality), the ceremony was believed to be in honor of Fanus.
Another unique custom of Feast of Lupercalia was the pairing of young boys and girls who otherwise lived a strictly separated lives. During the evening, all the young marriageable girls used to place a chit of their name in a big urn. Each young man used to draw out a name of a girl from the urn and became paired with that girl for the rest of the year. Quite often, the paired couple would fall in love and marry.
Later, when Christianity spread through Rome, the custom of finding a mate through lottery was deemed un-Christian and outlawed. People felt that mates should be chosen by sight and not luck. Around 498 AD, Pope Gelasius declared 14th February as Valentine's Day to honor saint Valentine of Rome - the patron saint of love and lovers. Even in present time lovers all over the world celebrate the festival of Valentine's Day with joy and verve.