Valentine's Day as we know it is a holiday driven by greeting cards, roses and fancy dinners.

But it wasn't always that way. The holiday actually has rather dark and mysterious beginnings. Here are some of the theories about how Valentine's Day may have began.

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We don't really know who the actual St. Valentine was.

He could be one of at least three different saints with Valentine-related names. According to the History Channel, all of them were martyred.

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St. Valentine may or may not have been a secret romantic.

The most romantic legend says Valentine conducted marriage ceremonies for young lovers in secret after Emperor Claudius II of Rome decided unmarried men made for better soldiers and outlawed marriage for young men, and Valentine was put to death when his crimes were discovered.

Other stories claim Valentine sent the first "valentine" greeting when he fell in love with a young girl while imprisoned for helping Christians escape Roman prisons.

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The modern holiday could be linked to an ancient pagan festival.

Historians say Valentine's Day may be celebrated in February to provide a Christian alternative to a pagan celebration called Lupercalia, which was classically celebrated on Feb. 15. The festival involved Roman priests sacrificing goats and dogs and using their hides to gently slap women as a fertility blessing.

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The official holiday dates back to the 5th Century.

Pope Gelasius declared Feb. 14 as St. Valentine's Day, but it wasn't originally considered a day for romance.

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The oldest known valentine dates back to 1415.

It was a poem written by Charles, the Duke of Orleans, to his wife while he was imprisoned in the Tower of London. He was 21 and had been captured at the Battle of Agincourt. He was imprisoned for more than 20 years.

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