The whole green man controversy reminds me of Lada and Lel. Who, you ask? Supposedly, two ancient Slavic fertility gods, whose worship was preserved in circle dances (khorovods, like the Balkan Hora). Village women would dance singing refrains like lada, lel.
19th century folklorists with paganism on the brain were straining to find pre-Christian origins for everything, even to the extent of inventing old gods.