The origins of Valentine’s Day, like the origins of love itself, are somewhat obscure — a combination of myth, history, destiny, chance and marketing.
Legend has it that a certain third-century priest named Valentine persisted in performing marriage ceremonies despite a ban by the Roman emperor Claudius II (Claudius was persuaded that single men made better soldiers for his army). Thrown into jail, Valentine formed a relationship with his jailor’s daughter (some say he cured her blindness) and he signed his last message to her "From your Valentine," a phrase which still gets a lot of mileage.
St. Valentine was executed on February 14, circa the year 270, and his remains (probably his, but there were two other Christian martyrs called Valentine) are now on display in the Whitefriar Street Carmelite Church in Dublin.
There are also reports of an ancient pagan custom that took place in preparation for the Roman festival of Lupercalia, which started February 15. The names of the town’s maidens would be collected and then drawn at random by the local bachelors; in this fashion couples were paired off for the year.
Third, medieval Europeans thought February 14 was the date on which the birds started to mate. (There’s no record of when the bees started.) From "Parlement of Foules," a poem by Chaucer:
"for this was on seynt Volantynys day/ Whan euery bryd comyth there to chese his mate.
Starting on Valentine’s Day 1400, the French royal court held a Cour Amoreuse, in which ministers met after mass in "joyous recreation and talk about love." Love poems were presented before the ladies, who judged them and awarded a golden crown for the best one.
The first valentine on record was sent in 1415 by Charles, duke of Orleans, to his wife while he was imprisoned in the Tower of London. That message is on display in the British Library. In the 1840s a Massachusetts woman called Esther Howland came up with the idea of mass-producing Valentine’s Day cards; now, about a billion are sent yearly, mostly by women.
Valentine’s Day gifts, however, are another matter — there, American men outspend women two to one. The most popular gifts, according to the National Retail Federation, are (in descending order): candy/chocolate, dinner/a night out, flowers, and jewelry.