First, some excerpts from Wikipedia about the historical/mythological Rhiannon:
Rhiannon is a prominent figure in Welsh mythology, mother to the Demetian hero Pryderi and wife to Pwyll... Upon ascending the magical mound of Gorsedd Arberth, the Demetian king Pwyll witnesses the arrival of Rhiannon, appearing to them as a beautiful woman dressed in gold silk brocade and riding a shining white horse...Now, on to the song:
Under the advice of his noblemen, Pwyll and Rhiannon attempt to supply an heir to the kingdom and eventually a boy is born. However, on the night of his birth, he disappears while in the care of six of Rhiannon's ladies-in-waiting. To avoid the king's wrath, the ladies smear dog's blood onto a sleeping Rhiannon, claiming that she had committed infanticide and cannibalism through eating and "destroying" her child. Rhiannon is forced to do penance for her crime...
The Mabinogi do not present Rhiannon as anything other than human. Scholars of mythology have nevertheless speculated that Rhiannon may euhemerize* an earlier goddess of Celtic polytheism. Similar euhemerisms of pre-Christian deities can be found in other medieval Celtic literature, when Christian scribes and redactors may have felt uncomfortable writing about the powers of pagan gods...
According to Miranda Jane Green, "Rhiannon conforms to two archetypes of myth - a gracious, bountiful queen-goddess; and as the 'wronged wife', falsely accused of killing her son."
Nicks discovered Rhiannon through a novel called Triad, by Mary Leader. The novel is about a woman named Branwen, who is possessed by another woman named Rhiannon. There is mention of the Welsh legend of Rhiannon in the novel, but the characters in the novel bear little resemblance to their original Welsh namesakes... Nicks bought the novel in an airport just before a long flight and thought the name was so pretty that she wanted to write something about a girl named Rhiannon... After writing the song, Nicks learned that Rhiannon originated from a Welsh goddess, and was amazed that the haunting song lyrics applied to the Welsh Rhiannon as well.... Nicks avoided wearing black clothing for "about two years" in an effort to distance herself from the witchcraft and dark arts associations surrounding her as a result of the lyrics to "Rhiannon" giving fans the wrong impression.This post was prompted by my recent viewing (and recording) of the VH1 Behind the Music Remastered segment on Fleetwood Mac:
* "Euhemerize" was a new word to me, explained here.