islet
陼 centers on a small island or islet, a piece of land surrounded by water.
陼 combines the mound radical ⻖ (阜, suggesting a raised landform) with 者, which likely contributes the sound. The character is used for a small island or islet.
The left side ⻖ suggests a mound or hill, and the right side 者 looks like a person sitting on something. Picture a person sitting on a small mound of land surrounded by water: an islet.
For ショ, imagine a small show being performed on the islet: show -> ショ, and the performer stands on the tiny island.