I went to far too much trouble to make this image. But it IS the feast of St. Valentine and people DO give each other hearts. I just put two and two together. Some day my sense of humor is going to land me in a lot of trouble. Maybe today.
There was more than one St. Valentine. On February 14 we honor Valentine of Rome and Valentine of Terni, although almost nothing is known of these gentlemen except that they were martyrs and Valentine of Rome was buried on February 14th.
Although some folks claim that this observance was a Christian assumption of the fertility rites of the ancient Roman festival of Lupercalia, there's no evidence that this was the case. Rather, the co-incidence of the dates is just that... co-incidence. Lupercalia was abolished in the Fifth Century by Pope Gelasius, who didn't replace it with anything.
Hearts don't really look like this.
Of course, you knew this already. So did ancient artists. In antiquity, hearts were depicted as being more anatomically correct. The stylized heart symbol is an invention of the Middle Ages, which may have been popularized by its use on playing cards. But even as late as the 18th century, sacred hearts were drawn as being anatomically correct in ecclesiastical art.
The sending of flowers, chocolates, and greeting cards are all British innovations, but one of their traditions hasn't quite made it into the worldwide main stream... Jack Valentine. You might think of him as a cross between Father Christmas and the Easter Bunny with really bad press. In Norfolk, on February 14th, Jack Valentine would leave gifts at the back door, knock loudly, and then run like hell. Sound creepy? Still, I prefer it to the similar practice in the US of leaving a flaming bag of dog poo.
Finally, here's a fun little song that was written with Valentine's Day in mind: