Anything bubonic has to do with inflamed lymph nodes. Symptoms of the bubonic plague include painful, hugely swollen nodes.
We've got lymph nodes all over our body, including in the groin area — and the word bubonic derives from the Greek boubon, "groin." The word was commonly used for any swelling of the infection-fighting nodes until the 1820s, when it came to almost universally refer to the bubonic plague. Before antibiotics, this highly infectious disease killed up to 90 percent of those who were infected.