Common comfrey, also known as Symphytum officinale, has a variety of synonyms that can be used to refer to this herb. These synonyms include knitbone, blackwort, bruisewort, slippery root, and gum plant. The common name 'knitbone' derives from the traditional use of comfrey to promote healing of broken bones. 'Blackwort' refers to the dark roots of the plant, while 'slippery root' is another reference to the same feature. 'Bruisewort' highlights the plant's use in treating bruises, and 'gum plant' is a nod to its reputation as an effective treatment for gum disease. All these synonyms are interchangeable and can be used depending on personal preference or context.