As with most modern holidays & celebrations, the roots are in pagan traditions. I loved what I found on this website about St. Valentines Day:
The history of Valentine’s Day and its patron saint is shrouded in mystery. But we do know that February has long been a month of romance. St. Valentine’s Day, as we know it today, contains vestiges of both Christian and ancient Roman tradition.
Today’s celebration of Valentine’s Day grew out of a tradition that began many years ago in ancient Rome. A Roman feast of Lupercalia was celebrated on February 15. This ancient festival involved the celebration of fertility and honored two Roman gods, Juno and Pan. One of the conventions of this occasion called for young maidens to write love messages. The messages were placed in a large urn and then drawn out by unmarried men who courted the fair maidens whose messages they had chosen.
