apparently, the green man is a recent name and it is possible that it might actually be cernunnos, the horned celtic god of the wild. the christian religion adopted cernunnos' look and gave it the name "satan" to represent all evil.
cernunnos may be the father god of the wiccan beliefs. although by father god they do not mean creator god, but father god while aradia is the mother god and the creator of them is simply known as "the one"