The name of the second month of our present calendar is derived from a festival dating back to the Sabines, an ancient tribe from central Italy who were conquered by the Romans around 290 BC. The festival was a fertility ritual in which the women were flogged with an appendage, or organ, of an animal (sorry, I'm not sure what) with the supposed result that they would be more likely to bear children. It is through association with this festival that the romantic associations of St. Valentine's Day began, a day that originally had no association with love or relationships.
The original Roman calendar did not include February. It consisted of only ten months and began with March. The creator of the Roman calendar is unknown (legend says it was the mythical Romulus). Around 700 BC Numa Pompilius added the months of January and February.