Originally: the plant butterbur, Petasites hybridus. Later also: (in form Petasites) a genus of the family Asteraceae (Compositae), comprising perennial herbs, usually with large leaves and small white, yellow, or pink flowers, native to north temperate zones; (also petasites) any member of this genus, especially butterbur or winter heliotrope, P. fragrans.
Valid publication of the genus name: P. Miller Gardeners Dict. (1754) (ed. 4) s.v.
Mid 16th century; earliest use found in William Turner (d. 1568), naturalist and religious controversialist. From post-classical Latin petasites from Hellenistic Greek πετασίτης, variant of πετασῖτις from πέτασος + -ῖτις, so called on account of the shape of the leaves.