Aspens are trees of the willow family and are closely related to poplars. Some species, in fact, are alternatively known by both names.
The aspen tree's quivering leaves are, in Christian lore, said to be the result of arrogance at the Crucifixion because the aspen did not tremble like other trees. A German version claims that the aspen was the only tree to refuse to acknowledge Jesus' divinity. The cross that Christ was crucified on is sometimes said to have been aspen wood. It is also sometimes said that aspen leaves are made from female tongues and their quivering is due to women's inability to stop talking.