Lupercalia was a Roman holiday held in mid-February which honoured Faunus, the god of fertility, and the legendary founders of Rome, Romulus and Remus. The Luperci, male Roman priests, would head to the cave where the baby Romulus and Remus were believed to have been raised by a she-wolf. The Luperci would sacrifice a goat for fertility and a dog for purification. After splitting the goat's hide into strips and dipping it into the sacrificial blood, they would head to the streets of Rome and whip the women and the crop fields. This whipping was believed to make both women and fields more fertile. Young women would also place their names into a large urn: men would each choose a name, and the new pair would spend a year together and often end up married.
The historical Valentine(s)
The Roman emperor Claudius II supposedly banned marriages because too many young men were opting to get married purely to avoid being drafted into the army. Valentinus, a Christian priest, was caught performing Christian marriages in secret and was sentenced to death. While he awaited his execution, young lovers supposedly visited him and discussed how love was better than fighting.
Another Christian priest called Valentinus was supposedly jailed for helping other Christians to escape the harsh Roman jails. He fell in love with his jailor's daughter and sent her love notes, signing off with 'from your Valentine'.
There are many other stories about the 'original' Valentines in existence, but what they all have in common is a sympathetic, heroic and romantic man.
Christianisation of Pagan holidays
Throughout history Christianity has taken over Pagan celebrations, or reworked them to fit Christian ideals. In the 5th century the emperor Gelasius dedicated February 14th to the martyr(s) Valentinus rather than the Pagan god Faunus. Raucous elements were toned down, and instead of pulling women's names from an urn, both men and women would choose the names of martyred saints instead and aim to emulate them for the year.
The poetic renaissance
With the help of poets and playwrights such as Chaucer and Shakespeare, elements of love and fertility one again returned to Valentine's celebrations. In England and France it was commonly thought that February 14th was the beginning of the birds' mating season: the date came to be connected with love, sexuality and procreation once again.
Handmade paper cards, a traditional element of Valentine's Day, were introduced in the Middle Ages, and in 1913 Hallmark began mass producing Valentine's cards. Today, an estimated 1 billion Valentine's Day cards are sent each year.