Lord, bless Wikipedia, without which I would not have known about a far more ancient holiday at this time of year:
The festival began with the sacrifice by the Luperci (or the flamen dialis) of two male goats and a dog. Next two young patrician Luperci were led to the altar, to be anointed on their foreheads with the sacrificial blood, which was wiped off the bloody knife with wool soaked in milk, after which they were expected to smile and laugh.
The sacrificial feast followed, after which the Luperci cut thongs from the skins of the victims, which were called Februa, dressed themselves in the skins of the sacrificed goats, in imitation of Lupercus, and ran round the walls of the old Palatine city, the line of which was marked with stones, with the thongs in their hands in two bands, striking the people who crowded near. Girls and young women would line up on their route to receive lashes from these whips. This was supposed to ensure fertility, prevent sterility in women and ease the pains of childbirth. This tradition itself may survive (Christianised, and shifted to Spring) in certain ritual Easter Monday whippings.
On the one hand, it sorta makes putting Valentine's day cards into paper sacks look pretty tame. On the other, if given a choice between putting cards in sacks or being chased around the town square by bloodstained, half-naked lunatics flinging raw goatskin around... well, suddenly cards don't look so bad.