Woodkerns
Native Irish displaced by the Anglo-Norman invasion, operated as bandits in the forests of Ireland where they were known as "wood kerns" or Cethern Coille. They were such a threat to the new settlers that a law was passed in 1297 requiring lords of the woods to keep the roads clear of fallen and growing trees, to make it harder for wood kerns to launch their attacks.
Read more about this topic: Kern (soldier)