The genus name for comfrey is Symphytum, which means to "unite or knit together." The name com-firma means simply, "knitting of bones."
Comfrey contains a special substance called allantoin, which is a cell proliferative - this means it makes cells grow faster. This is one of the reasons why comfrey-treated bones knit so fast, wounds mend so quickly and burns heal with such little scarring. Comfrey is often called knitbone or healing herb.
Interally, comfrey root may be used to treat coughs or digestive disorders.