Mabon: MAH-bon
Welsh: mab
son, young man,
youth (n.)
1. "Divine Son" referring to the god Mabon ap Modron, cognate of Maponos.
The naming of the autumn equinox with "Mabon" is the invention of Aidan Kelly in the 1970s; he thought it sounded "ancient." He also apparently decided to call the summer solstice "Litha", but at least that has some basis in the old English calendar outlined by Bede. There is no literary or historical connection between Mabon ap Modron/Maponos and the autumn equinox.