The common names for the plants are all based on the previous usage of one species, "Eupatorium perfoliatum", as an herbal medicine. Despite its name, boneset is not used to treat broken bones, instead the common name apparently derives from the herb's use to treat dengue fever, which was also called breakbone fever because of the pain that it caused. The name thoroughwort also comes from "Eupatorium perfoliatum", and refers to the perfoliate leaves, in which the stem appears to pierce the leaf (i.e. go through, note that in older usage "thorough" was not distinguished from "through", compare for example the word thoroughfare).