The Autumn Equinox is a day that marks the first day of autumn astronomically.
There is no denying our ancestors would have felt a significant difference around this time of year. But specifically we just don't know for sure, unlike other holidays that were written down. Of course, many modern Pagans today - such as Wiccans and druids - find this moment in our calendar important to mark the first day of autumn.
There are some sites around the world that correspond with this time, such as Loughcrew in Ireland, which are a group of historic ancient tombs inside of large hills. The sun rises and sets just at the right point for it to beam through a gap, shining into the passage and onto art on the walls.
Mabon is usually a word associated with the autumn equinox within the Wheel of the Year. So where does it come from?
Well, Mabon used to mean the equinox was first used in 1970, referring back to 'Mabon ap Modron', a figure from Welsh mythology. Some will call him a Welsh god, but he more than likely has origins in his story influenced by deities. And although our ancestors probably acknowledged this time of the year, and probably had festivals around this time, it doesn't have any specific pagan origin unlike other holidays. It is usually considered the second harvest festival of the year, after Lughnasadh and before Samhain, where apples are harvested along with other nuts and berries.