How did Valentine's Day begin? With the whipping of women with the hides of recently slain dogs and goats in Ancient Rome :
From NPR :
From Feb. 13 to 15, the Romans celebrated the feast of Lupercalia. The men sacrificed a goat and a dog, then whipped women with the hides of the animals they had just slain.
The Roman romantics "were drunk. They were naked," says Noel Lenski, a historian at the University of Colorado at Boulder. Young women would actually line up for the men to hit them, Lenski says. They believed this would make them fertile.
The brutal fete included a matchmaking lottery, in which young men drew the names of women from a jar. The couple would then be, um, coupled up for the duration of the festival – or longer, if the match was right.