When the Tuatha Dé Danann went to the "Island of Destiny", six sisters went along with the other gods with three of them having one goal in mind, that being to have the new land named after them. Éiru ultimately won that. Over time her name was twisted in translation and changes to Éire, then to Ire. The land of Ire, or as it's known today; Ireland.
The idea behind this was to mix Irish mythology with some archeology. Weapons and other offerings were gifted to water springs throughout the Neolithic, Bronze Age and Ironage on the isles which is probably why spirals were used as decorations for thousands of years using either blue woad or carvings. "Celts" were pretty prone to collecting heads too. The idea was that the three sisters are asking for the Danu to name the island after them. Take the myths with a grain of salt though, they're mostly written by Christain scholars. I had fun carving stuff out in this though and mixing in all the archeology stuff.