Dian Cecht's curative well
Dian Cecht's 'boiling' of the River Barrow
It was Dian Cecht who once saved Ireland, and was indirectly the cause of the name of the River Barrow. The Morrígú, the heaven-god's fierce wife, had borne a son of such terrible aspect that the physician of the gods, foreseeing danger, counselled that he should be destroyed in his infancy. This was done; and Diancecht opened the infant's heart, and found within it three serpents, capable, when they grew to full size, of depopulating Ireland. He lost no time in destroying these serpents also, and burning them into ashes, to avoid the evil which even their dead bodies might do. More than this, he flung the ashes into the nearest river, for he feared that there might be danger even in them; and, indeed, so venomous were they that the river boiled up and slew every living creature in it, and therefore has been called the River Barrow, the ‘Boiling’ ever since.
Dian Cecht's healing of Nuada's arm
He made King Nuada a silver arm which could move and function as a normal arm. Later, Dian Cecht's son, Miach, replaced the silver arm with an arm of flesh and blood, and Dian Cecht killed him out of professional envy. Miach's sister, Airmed, mourned over her brother's grave. As her tears fell, all the healing herbs of the world grew from the grave. Airmed arranged and catalogued the herbs, but then Dian Cécht again reacted with anger and jealousy and scattered the herbs, destroying his daughter's work as well as his son's. For this reason, it is said that no human now knows the healing properties of all the herbs.
Linguistic knowledge about regular sound changes in Celtic languages (McCone, 1996) and analysis of the University of Wales’ Proto-Celtic lexicon and of Julius Pokorny’s Indogermanisches etymologisches Wörterbuch permit *Deino-kwekwto- ‘swift concoction’ as a plausible Proto-Celtic reconstruction for this theonym.