23 December 2015
This flower (Euphorbia pulcherrima), native to Mexico and associated with Christmas, has a rather straightforward etymology. It is named after Joel Roberts Poinsett, who served as the U. S. minister (i. e., ambassador) to Mexico from 1825–30. An amateur botanist, Poinsett sent samples of the flower back to the States, and the name poinsettia became attached to the plant by 1836. The original Latin designation was Poinsettia pulcherrima, but by the 1860s it was recognized as being in the genus Euphorbia.
The association with Christmas began in Mexico. In Mexican Spanish the poinsettia is called flor de Noche Buena (Christmas Eve flower).
Sources:
Oxford English Dictionary Online, third edition, September 2006, s. v. poinsettia, n.