Deadly nightshade is Atropa belladonna, and both parts of the name are worth reading. The genus honours Atropos, the eldest of the three Greek Fates, the one who cuts the thread of life, a botanist's frank acknowledgement that the plant kills. The species name, belladonna, beautiful woman, records the Renaissance cosmetic use of its juice to dilate the pupils, which was thought becoming; the active compound, atropine, still dilates the pupil in the eye clinic today. All parts of the plant are highly toxic, the glossy black berries most temptingly so, and it is among the most notoriously poisonous plants of Europe. This is stated as fact and warning, not as folklore.
Atropine's modern medical role goes well beyond the eye clinic use noted above: because it blocks the same nerve receptors that organophosphate nerve agents and pesticides overstimulate, atropine is the standard emergency antidote for that class of poisoning, carried in military and civilian auto-injectors precisely for this purpose, so a compound first isolated from a plant famous for killing is now issued specifically to save lives against a chemical threat unknown to the herbalists who first studied it. Deadly nightshade belongs to the family Solanaceae, the same botanical family as the tomato, potato, eggplant and chilli pepper, ordinary food crops that share its underlying chemistry closely enough that unripe green potatoes and nightshade-family foliage can themselves carry toxic alkaloids in smaller, usually non-lethal amounts.