red bark
/ˌrɛd ˈbɑːk/noun
1A reddish form of cinchona bark used medicinally as a source of quinine, specifically that obtained from Cinchona pubescens (formerly called C. succirubra).
2More fully red bark tree. The tree Cinchona pubescens.
Origin
Late 18th century; earliest use found in William Saunders (1743–1817), physician. From red + bark.