1As the name of a plant. Originally and chiefly Jamaican. Any of several tropical American shrubs, often having aromatic foliage used medicinally; especially Chromolaena odorata (family Asteraceae) and black sage, Cordia curassavica.
2 rare At May Day celebrations, formerly especially among chimney sweeps: (a name for) a man or boy wearing a wooden or wicker framework in the shape of a rounded cone or a pyramid, which is decorated with leaves to symbolize seasonal fertility; = Jack in the green .
Early 18th century; earliest use found in Henry Barham (?1670–1726), botanist. In some forms from Jack + in + the + bush.