The origin of this practice is believed to be with the Sami people.  They fashioned darts made from lead and would throw the darts to inflict pain or trouble on an enemy.  This would be akin to the actions used with a Voodoo doll, but predate the Voodoo doll considerably. 

The darts are around 2"-3" in length and the practice of inflicting the pain vary through time.  It is likely practice developed or evolved as the Sami people have been around since the 1st-2nd century.

One practice involved envisioning the enemy as you throw the dart, to draw a likeness of enemy or write their name and throw the dart to the drawing, or to wrap the dart with a piece of cloth that had the enemy's name and throw the dart.

All measures prove effective.  As lead is now known to be a toxic substance, this is not a recommended practice.