Originally known as St. Valentine's day, it was shortened over the years, but the thought is still the same. It's a day to celebrate love. The day is supposedly named after an early Christian martyr (or possibly several) by the name of Valentine. They really had no romantic association. It was first associated with romantic love during the Middle Ages when courtly love was popular.
Geoffrey Chaucer wrote "For this was Saint Valentines Day, when every bird cometh there to choose his mate". The same words were included in a poem that honored the engagement of King Richard II to Anne of Bohemia. Chaucers reference to Valentines Day would not explain the date - since February is not the time of year for bird mating. Chaucer makes it seem like an old traditin, although it doesn't appear to have existed prioer to his writing about it.
Where would love be without a little mystery?
Paris, the city of love, adopted a High Court of Love on February 14, 1400. This was run by women based on their poetry reading and writing abilities. The holiday flourished and England embraced the celebration with the forming of factories that assembled paper valentines.
Then of course, the hand written form gave way to the capitalization by numerous industries - candy, flowers, cards. It is now estimated that 190 million valentines are sent each year just in the U.S.
In my house when I was in grade school it was a flurry of activity to make sure you had a card for every child and taping those chalky hearts to your "special" friends.
May you all feel the love today!