Piru

A Piru is a minor evil spirit or Demon in Finnish mythology.

In folklore the Piru often features as a nasty spirit of the forest with which a wise-aleck either wins or loses a battle of wits, giving or receiving a forfeit in return.

The Devil is often referred to as Pääpiru, literally "Headpiru".

"Piru" is also a mild swearword in Finnish.