This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The historical origin of 墼 is uncertain. It visually contains 土 (earth) at the bottom and a complex upper component that may relate to striking or breaking, but the exact development is unclear.
With no clear meaning, focus on the shape: 土 at the bottom suggests earth, while the upper part looks like a tool striking something. Picture a tool striking the earth, perhaps to break it apart.
For ゲキ, imagine a gecko (ゲキ) striking the earth with its tail: gecko -> ゲキ, and the earth 土 shakes.
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