In Welsh folklore, there is a figure known as Mabon ap Modron, or Mabon son of Modron. He appears in some of the Arthurian legends, as one of Uther Pendragon’s loyal servants, and as a follower of Arthur himself.
Also of note, there was a female Cornish saint named Mabyn, to whom the founding of St. Mabyn’s Church is dedicated, although there is speculation that the church was actually started by the Welshman, Mabon, rather than the female martyred saint. Mabyn’s festival is celebrated on November 18, approximately halfway between the autumn equinox and the winter solstice.
There is much discussion in the Pagan community as to whether one of these figures provide the name of the autumn equinox holiday, Mabon. Interestingly, it appears that the tradition of calling the autumn equinox by the name Mabon goes back only to around 1970, when author Aidan Kelley wrote was gathering information for his 1991 book, Crafting the Art of Magic, and assigned new names to the Sabbats, most of which were rooted in Celtic lore. The purpose, Kelly has said, was to conceptualize modern Pagan religious ceremonies.
Historian Ronald Hutton has pointed out that there is no academic evidence indicating that ancient Celts called their equinox celebration Mabon.
In Druidic traditions, the autumn equinox was referred to as Alban Elfed, meaning the light of the water. This name refers to a time of year in which the balance of light and dark shifts, so that the darkness begins to take over.