The song is always referred to as simply "Rhiannon" on Fleetwood Mac albums. The title "Rhiannon (Will You Ever Win)" was used only on single versions in some countries.
Live performances of the song were sometimes prefaced with Nicks saying, "This is a story about a Welsh witch." During 1975–1980, Fleetwood Mac's live performances of "Rhiannon" took on a theatrical intensity not present on the FM-radio single. The song built to a climax in which Nicks' vocals were so impassioned that, as drummer and band co-founder Mick Fleetwood said, "her Rhiannon in those days was like an exorcism."
Nicks discovered Rhiannon in the early '70s through a novel called Triad, by Mary Bartlet 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 (both Rhiannon and Branwen are major female characters in the medieval Welsh prose tales of the Mabinogion).
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. She wrote "Rhiannon" in 1974, three months before joining Fleetwood Mac, while living with Richard Dashut and Lindsey Buckingham in Malibu, and has claimed that it took 10 minutes to write.
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 researched the Mabinogion story and began work on a Rhiannon project, unsure of whether it would become a movie, a musical, a cartoon, or a ballet. There are several "Rhiannon Songs" from this unfinished project including "Stay Away" and "Maker of Birds." Nicks wrote the Fleetwood Mac song "Angel" based on the Rhiannon story.