pine tree
枌 centers on a specific type of pine tree, used for its wood or as a tree name.
枌 combines 木 (tree) with 分, which likely contributes the sound. The exact historical development is uncertain, but it is a phono-semantic compound for a type of pine.
A tree 木 that divides 分 into pine planks: 枌 is a pine tree used for its wood.
For ショウ, imagine a pine tree growing under a showy spotlight: show -> ショウ, and the pine tree 枌 stands out.