Which element of an amputated virgin breast healing a snakebite is a "Celtic theme"?

Question

The Breton folk song Gwerz Santes Enori has survived for centuries as an oral tradition combining storytelling with music. Its story, quoting Wikipedia's summary, begins like this:

The poem's story concerns the youngest of a king's three daughters (the king of Brest, or Brittany, or Spain, depending on the version), who sacrifices herself when her father is bitten by a snake. Only a virgin breast can save him, and Enori, the youngest, neglected daughter, offers herself up after her two sisters refuse. When she goes to help him a snake jumps onto one of her breasts, and her father cuts off the breast, after which he is miraculously cured (Mary-Ann Constantine identifies this as a "Celtic theme"^[1]); the daughter is rewarded by an angel who brings her a golden breast, and she gets a husband as well.

Which element of this story is said to be a "Celtic theme"? The cited source goes to a Google Books version of Celtic Culture: A-Celti edited by John T. Koch, but I tried searching it for the phrase "Celtic theme" and didn't find anything relevant.

Answer 1

The footnote in the citation goes to the sub-heading Breton within the entry for Ballads and Narrative Songs in Celtic Culture: A Historical Encyclopedia, ed. John T. Koch (Santa Barbara: ABC-CLIO, 2005), vol. 1: A-Celti. The sub-heading includes the following:

A small number of songs have notably Celtic themes: the gwerz of Santes Enori (Saint Enori), which tells the story of a princess who saves her father by sacrificing her breast to a snake, contains elements of a narrative complex identifiable in a Latin saint's life, a Welsh triad (see TRIADS), a Scottish Gaelic folk tale (see FOLK TALES) and a medieval French romance. (p. 163)

A triad is a bardic narrative that is built around three names and summarizes a larger tale. Presumably an extant Welsh triad, as well as some Scottish folk tale, involves elements also found in the story of Enori, such as a sick king, or a self-sacrificing daughter, or a snakebite. Perhaps the triad and/or folk tale in question specifically refer to Enori. Unfortunately the associated entries under Triads (in Volume V) and Folk Tales (in Volume II) do not appear to mention this particular song specifically, so I have been unable to identify these elements more precisely. However, it appears that the narrative material of the song includes some elements that are also found in Welsh and Scots Gaelic, hence Celtic themes.