grieved, distressed in mind
忉 centers on a state of mental distress or grief: feeling deeply troubled or sorrowful in mind.
忉 combines the heart radical 忄 with 刀, which likely provides the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound where the heart component indicates the mental or emotional domain.
The heart radical 忄 beside a blade 刀: imagine a heart being cut by a knife, causing deep grief and distress.
For トウ, picture a grieving person touching their heart and letting out a long, sorrowful 'toe' sound: toe -> トウ, as the heart is cut by the blade.