Nechtan is an ancient Irish water deity, keeper of the well of wisdom. Only Nechtan and his three cupbearers were allowed near the well and no else. Nechtan wife Boann defied this taboo, visiting the well with fatal consequences. The name Nechtan comes from the root word meaning to wash was once very popular shared by several Pictish kings as well as a saint that is associated with a holy well. A site that is sacred to Nechtan was his well Sidh Nechtan source of the Boyne River.
Judika Illes, Encyclopaedia of Spirits the ultimate guide to the magic of fairies, genies, demons, ghosts, gods and goddesses, 2009, Nechtan, p 748