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After the obsolete genus name Poinsettia, named after Joel Roberts Poinsett (19th-century US minister to Mexico); equivalent to Poinsett + -ia.
Etymology from Wiktionary, CC BY-SA 4.0.
poinsettia
Today it means: A plant, Euphorbia pulcherrima, with rather small and insignificant flowers surrounded by large bright red leaves; native to Mexico and Central America and widely cultivated as a garden plant; widely used in Christmas floral displays. Full definition →