and Maypoles are remnants of the Scandinavian Ash, called Yggdrasil', the Tree of Time, whose roots penetrate to heaven, Niffheim and Ginnungagap (the gap of gaps). In Ginnungagap the frost giants dwell, in Niffheim is the great serpent Nidhögg; and under this root is Helheim, the home of the dead. We are told that the ancient Egyptians, at the Winter Solstice, used a palm branch containing twelve leaves or shoots to symbolise the “completion of the year.” The modern custom comes from Germany.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Christmas Trees from Fact Monster: