It has been fortified in historical times since the early 12th Century CE when the invading Normans built a mote and bailey on what was probably originally a neolithic passage grave similar to Newgrange. In Irish cosmology, it is often assumed to be the burial place of Amhairgin mac Míled, whose name ("Amhair" = singing; "gin" = give birth) indicates that in ancient Irish mythology he was regarded as the originator of the arts of song, poetry and music. The shamanistic Early Irish poem "The Song of Amhairgin", uttered by him in the story of his entry into Ireland by the River Boyne, was therefore conventionally regarded as the first Irish poem.