In Welsh mythology, Elffin ap Gwyddno (Welsh, also Elphin) was a son of Gwyddno Garanhir, 'Lord of Ceredigion'. The earliest example of the name occurs in several of the mythological poems attributed to Taliesin in the Book of Taliesin. The date of their composition is uncertain but probably predates the Norman conquest. Several late medieval compositions refer to Elffin and Taliesin in more detail.
The name Elffin/Elphin may possibly be cognate with two Irish words "Aill Fion" meaning "Bright Cliff" or "Bright Rock".
Read more about Elffin Ap Gwyddno: Hanes Taliesin