The Bubonic Plague, or Black Plague/Black Death, is called that because the bacteria's toxin affects the Red Lymph Nodes, which are called Bubos, and causes them to swell. Hence, the Bubo-nic plague. Hope this helps.
The black death, other wise known as the Bubonic Plague occurred in Europes middle ages. It was caused by a disease that rats and fleas carried and as shown, was deadly, for there was no cure for it then
The Bubonic plague is called bubonic because it comes from the Greek word boubōn, meaning swelling. Since the swelling of the lymph nodes is the most common symptom of the bubonic plague, this is the term used.