Creirwy is known from celtic folklore in the "Ystoria Taliesyn" (the tale of Taliesyn) where she is the daughter of Tegid Foel and Cerridwen. She is described as the fairest maiden in the entire world, a figure of proverbial beauty, 'the loveliest nymph of the earth.' Her brothers were the ugly Afagddu and the handsome Morfran. Creirwy's name may be derived from the Cymric word creider meaning 'purity' whereas rhwy is an old celtic term for 'purity' so that her name could mean 'The Purest'; may also translate as 'a token; a jewel.'