Although the Garden of Eden was home to the Tree of Life and the Tree of the Knowledge of Good and Evil, the central tree or axis mundi (world axis) is also a great archetype of human thought, from totem poles in the Pacific Northwest to Mesopotamian ziggurats. For the Celts, however, the central tree was particularly meaningful. The word Druid, the word used to refer to the learned class in ancient Celtic society, may itself have come from the word for "knowing or finding the oak tree" and their early gatherings took place in clearings in the forest. Although there is no direct connection between the Tree of Life motif used to symbolize Christ in the illustrated manuscripts and the importance of the tree to ancient Celtic Druids, it is interesting to speculate that the image, if not the concept, has resonated for millennia in Celtic thought and design.