They say the holiday of Valentine's Day  derives it's origins
from the ancient Roman feast of Lupercalia.
In the early days of Rome, fierce wolves roamed the woods
nearby and the  Romans called upon one of their gods,
Lupercus, to keep the wolves away.
On February 15th, a spring festival was held in honor of Lupercus.
(Calendars were different at that time, which explains it being a spring festival)

One of the customs of the young people was name drawing.
On the eve of the festival of Lupercalia the names of Roman girls
were written on slips of paper and placed into jars.
Each young man drew a slip. The girl whose name was chosen was to
be his sweetheart for the year

Legend has it that the holiday was named after a Roman priest by the
name of Valentine,
in the days when Christianity was a new religion.
The Emperor at that time, Claudius II, ordered the Roman
soldiers NOT to marry or become engaged. Claudius
believed that as married men, his soldiers would want to
stay home with their families rather than fight his wars.
Valentine defied the Emperor's decree and secretly
married the young couples. He was eventually arrested,
imprisoned, and put to death

Valentine was beheaded on February 14th, the eve of the
Roman holiday Lupercalia. After his death, Valentine was
named a saint. As Rome became more Christian, the
priests moved the spring holiday from the 15th of
February to the 14th - Valentine's Day. Now the holiday
honored Saint Valentine instead of Lupercus