The correct rendering of this name in Modern Welsh depends on the specific source. The Middle Welsh avanc of Llyn Barfog is afanc in Modern Welsh, a word which is now used to mean "Beaver". The form avanc/afanc is also used in the Red Book of Hergest and most other medieval sources. In the Middle Welsh version of Peredur's tale, in the White Book of Rhydderch, the creature in the cave is called the addanc. Afanc is by far the most common spelling.