Souterrains, from the French “beneath the ground,” were built in the Early Christian period in Ireland as escape routes from invading Vikings (or the plundering clan nearby), and may also have been used as safe places to store the family's valuables.

What is the purpose of a Souterrain?

Souterrain (from French sous terrain, meaning "under ground") is a name given by archaeologists to a type of underground structure associated mainly with the European Atlantic Iron Age. These structures appear to have been brought northwards from Gaul during the late Iron Age.

What is the meaning of souterrain?

: an underground passage or chamber.