Treebeard is an embodiment of an ancient wisdom. The countenance of Treebeard displays this wisdom.
Wizardly nose. Treebeard has the nose of a Wizard. In fact there is something of a wizardly bearing about this oldest living thing. There is an air of Gandalf about Treebeard.
Amber eyes. The eyes of Treebeard are of amber. Amber is one of the most ancient of substances. Amber has been seen to trap insects in prehistoric times, preserving them over time. The amber eyes of Treebeard have seen many things over time. The wisdom of Treebearsd is contained in these eyes, preserved within his sap.