plies that they were called "Mistletoe
men."[677] If _bile_ (tree) is connected with the name Bile, that of the
ancestor of the Milesians, this may point to some myth of descent from a
sacred tree, as in the case of the _Fir Bile_, or "men of the
tree."[678] Other names like Guidgen (_Viduo-genos_, "son of the tree"),
Dergen (_Dervo-genos_, "son of the oak"), Guerngen (_Verno-genos_, "son
of the alder"), imply filiation to a tree. Though these names became
conventional, they express what had once been a living belief. Names
borrowed directly from trees are also found---Eburos or Ebur, "yew,"
Derua or Deruacus, "oak," etc.

The veneration of trees growing beside burial mounds or megalithic
monuments was probably a pre-Celtic cult continued by the Celts. The
tree embodied the ghost of the person buried under it, but such a ghost
could then hardly be differentiated from a tree spirit or divinity. Even
now in Celtic districts extreme veneration exists for trees growing in
cemeteries and in other places. It is dangerous to cut them down or to
pluck a leaf or branch from them, while in Breton churchyards the yew is
thought to spread a root to the mouth of each corpse.[679] The story of
the grave of Cyperissa, daughter of a Celtic king in the Danube region,
from which first sprang the "mournful cypress,"[680] is connected with
universal legends of trees growing from the graves of lovers until their
branches intertwine. These embody the belief that the spirit of the dead
is in the tree, which was thus in all likelihood the object of a cult.
Instances of these legends occur in Celtic story. Yew-stakes driven
through the bodies of Naisi and Deirdre to keep them apart, became
yew-trees the tops of which embraced over Armagh Cathedral. A yew sprang
from the grave of Baile Mac Buain, and an apple-tree from that of his
lover Aillinn, and the top of each had the form of their heads.[681] The
identification of tree and ghost is here complete.

The elder, rowan, and thorn are still planted round houses to keep off
witches, or sprigs of rowan are placed over doorways--a survival from
the time when they were believed to be tenanted by a beneficent spirit
hostile to evil influences. In Ireland and the Isle of Man the thorn is
thought to be the resort of fairies, and they, like the woodland fairies
or "wood men" are probably representatives of the older tree spirits and
gods of groves and forests.[682]

Tree-worship was rooted in the olde