bend, droop, undulate, to entwine, to be clad in
樛 centers on a bending, drooping, or undulating motion, often applied to trees or plants. The entwining and clad-in senses extend this idea to things that wrap around or cover by curving.
樛 combines 木 (tree) with 翏, which likely contributes the sound and the idea of bending or entwining. The exact historical development of 翏 is uncertain, but the character is associated with curved, drooping growth.
A tree 木 with the right side 翏, which looks like feathers bending and drooping. Picture a tree whose branches are so heavy with leaves that they bend and entwine around each other.
For キュウ, imagine a tree bending into a perfect curve, like the letter Q: Q -> キュウ, and the tree's drooping branches form that same rounded shape.