shrub
樕 refers to a shrub, a low woody plant smaller than a tree.
樕 combines 木 (tree/wood) with 欶, which likely contributes the sound. The exact historical development of 欶 is uncertain, but the character is used for a type of shrub.
The left side is a tree 木, and the right side 欶 looks like a bundle of twigs. Picture a small woody plant that is more than a single twig but less than a full tree: a shrub.
For ソク, imagine a shrub so thick you have to sock it with a machete to get through: sock -> ソク.