The origin of St. Valentine, and how many St. Valentines there were, remains a mystery. One opinion is that he was a Roman martyred for refusing to give up his Christian faith. Other historians hold that St. Valentine was a temple priestjailed for defiance during the reign of Claudius. Whoever he was, Valentine really existed because archaeologists have unearthed a Roman catacomb and an ancient church dedicated to Saint Valentine. In 496 AD Pope Gelasius marked February 14th as a celebration in honor of his martyrdom.
from catholic online
Of interest to me though, was how he became a symbol of love. Apparently Chaucer mentions it…
Jack B. Oruch writes that the first recorded association of Valentine's Day with romantic love is in Parlement of Foules (1382) by Geoffrey Chaucer. Chaucer wrote:wikipedia
For this was on seynt Volantynys day Whan euery bryd comyth there to chese his make.
["For this was on St. Valentine's Day, when every bird cometh there to choose his mate."]
and, as one might expect, it gets weird. Read the wiki entry and follow up on courtly love. haha
So the meaning changed over time and represents something now that has no 'justification' in the life of whichever St Valentine one is referencing. Rather, it may have started as a commemoration of the engagement of Richard II to Anne of Bohemia.
Never-the-less, postal rate drops and a straight laced Victorian England may have given rise to what we now know as Valentines Day.
Or the day of horror
A new tradition is being born, that of valentine's day revenges and killings and murders and horror.