BUTTERBUR
butterbur, bog rhubarb, Petasites hybridus, Petasites vulgaris
(noun) small Eurasian herb having broad leaves and lilac-pink rayless flowers; found in moist areas
Source: WordNet® 3.1
Etymology
Noun
butterbur (plural butterburs)
Any of several Eurasian herbs, of the genus Petasites, having dense clusters of often purple flowers.
Synonyms: butterdock, sweet coltsfoot
Source: Wiktionary
But"ter*bur`, n. (Bot.)
Definition: A broad-leaved plant (Petasites vulgaris) of the Composite
family, said to have been used in England for wrapping up pats of
butter.
Source: Webster’s Unabridged Dictionary 1913 Edition