persimmon
柹 centers on the persimmon fruit. It is a specific character for this fruit, with no broader abstract extensions.
柹 is a variant form of 柿, combining 木 (tree) with a phonetic component that likely represented the sound. The exact historical development of the right side is uncertain.
The left side 木 is a tree, and the right side looks like a fruit with a stem. Picture a persimmon hanging from a tree branch.
For シ, imagine a persimmon tree by the sea: sea -> シ, and the tree is full of ripe persimmons.