dig, dig out, gouge out, scoop
挖 centers on removing material by force: digging, gouging out, or scooping something from a surface or container.
挖 combines 扌 (hand) with 穵, which likely contributes both sound and the idea of hollowing out. The exact historical development of 穵 is uncertain.
The hand radical 扌 beside 穵 suggests a hand using a tool to dig or scoop. Picture a hand holding a small shovel, gouging out a hole.
For アツ, imagine digging at a stubborn root and grunting 'atsu!' with each scoop: atsu -> アツ.