keyaki, zelkova tree
欅 refers specifically to the keyaki tree, a type of zelkova. The meaning is a concrete tree name rather than an abstract concept.
欅 combines 木 (tree) with 擧, which likely contributes the sound. The character was created to name the keyaki tree.
The left side 木 is a tree, and the right side 擧 looks like a complex structure with many parts, like the spreading branches of a keyaki tree.
For キョ, imagine a keyaki tree shaped like a giant key: key -> キョ, and the tree unlocks the landscape.