What does "comfrey" mean?

Comfrey: A rough, hairy, perennial plant of several species, of the genus Symphytum. Note: A decoction of the mucilaginous root of the "common comfrey" (S. officinale) is used in cough mixtures, etc.; and the gigantic "prickly comfrey" (S. asperrimum) is somewhat cultivated as a forage plant.