One of the mysteries of the English language finally explained.
Definition of leaf cup in English:
leaf cup
noun
1Originally: (perhaps) a cup shaped like a leaf. In later use: a leaf folded and used as a cup, especially in Asia.
2Any of several plants of the American genus Polymnia (family Asteraceae), having each flower head in a cup of leaf-like scales; especially (more fully "white-flowered leaf cup") P. canadensis of eastern North America, a large perennial with lobed leaves (also called bear's-foot).
Origin
Early 18th century; earliest use found in The London Gazette. From leaf + cup.