be sad, grieve
慟 centers on deep, heartfelt sadness: grieving or being overcome with sorrow.
慟 combines the heart radical 忄 with 動, which likely contributes the sound and the idea of being moved emotionally, leading to grief.
The heart radical 忄 beside 動 (move) suggests a heart deeply moved by sorrow: 慟 is to grieve.
For ドウ, imagine a grieving person saying 'dough' as they knead bread to work through sadness: dough -> ドウ, and the heart is moved.