horse chestnut
桫 refers specifically to the horse chestnut tree. The meaning is narrow and botanical, without broader abstract extensions.
桫 combines 木 (tree) with 沙, which likely contributes the sound サ. The character was created to name the horse chestnut tree.
The tree radical 木 beside 沙 (sand) suggests a tree growing in sandy soil. Picture a horse chestnut tree thriving near a sandy riverbank.
For サ, imagine a horse chestnut tree growing in the Sahara: Sahara -> サ, and the tree's roots reach deep into the sand.