cut with a sword
斫 centers on cutting or chopping with a bladed weapon, specifically a sword. The single given meaning is a direct action of striking to sever.
斫 combines 石 (stone) and 斤 (axe), suggesting cutting or chopping with a stone axe or blade. The exact historical development is uncertain, but the component combination fits the meaning.
A stone 石 axe 斤 is used to cut with a sword-like chopping motion. Picture a heavy stone blade striking down to sever.
For シャク, imagine a shack being cut apart by a sword: shack -> シャク, and the blade chops through the wooden walls.