[Lucius Cornelius Sulla]

Wikipedia:
'In the United States and perhaps elsewhere, there is a common misconception that poinsettias are toxic. The origin of this could be found in the fact that most plants of the spurge genus are indeed toxic and also because the name of the plant seems to refer to the word poison. This misconception was spread by a 1919 urban legend of a two-year-old child dying after consuming a poinsettia leaf. While it is true that the plant is not very toxic, those sensitive to latex may suffer an allergic reaction and it is therefore not advisable to bring the plants into the home of sensitive individuals. If eaten, poinsettias may sometimes cause diarrhea and vomiting in animals and humans.'

[Lucius Cornelius Sulla]

The name, as we know, is from Ambassador Pointsett, not from poison.