So it seems that it's first appearance was featured on the work of Geoffrey of Monmouth's (1136) the Historia Regum Britanniae ("The History of the Kings of Britain") as the place where King Arthur's sword Excalibur (Caliburnus) was forged and later where Arthur was taken to recover from his wounds after the Battle of Camlann. Geoffrey called it in Latin Insula Avallonis in the Historia.
In his later work "Vita Merlini" he called it Insula Pomorum the "isle of apples", and dealt in more detail describing for the first time in Arthurian legend the enchantress Morgan le Fay as the chief of nine sisters who live on Avalon.
The name is generally considered to be of Welsh origin (though an Old Cornish or Old Breton origin is also possible), derived from Old Welsh abal, "apple", or aball, "apple tree". Maybe also influenced by Irish legends concerning the otherworld island home of Manannán mac Lir and Lugh, Emain Ablach (also the Old Irish poetic name for the Isle of Man)
Avalon was also known as the Avallach, the Isle of Apples, and the Otherworld, the Annwn.Thus it is told that the apples of Annwn (Avalon) healed all wounds.
In many legends of visits to the Otherworld, an outsider requires a special token to ensure safe passage to and from the land of fairies. This token is most often a branch of the Otherworld apple tree, a silver bough bearing blossoms and fruit that make music when shaken, often luring humans into enchanted sleep. This idea seems to come from older druidical practices, as early descriptions of the bards often mention the ritual use of silver branches hung with bells.
Celts like Norse, attributed the power of healing and youth, inmortality or rebirth, to apples. Apples are one of the magical trees, part of the Celtic Ogham tree alphabet, known as Quert. In Norse mythology the goddess Iðunn was the appointed keeper of golden apples that kept the Æsir young (or inmortal) forever.
Some Celtic Deities are associated to the "Apple": Morgan le Fay, and Cerridwen (maybe for her cauldron of rebirth). Some associate also Olwen, daughter and aunt of the giant Ysbaddaden on Welsh Mythology, maybe I guess for her appearance in the folktale Einion and Olwen, about a sheep herder who travels to the Otherworld to marry Olwen. The tale was collected at the turn of the 20th century but is certainly related to Culhwch and Olwen.
Photomanipulation by MorgainefromAvalon (all rights reserved by the author)