A "felon" is a an infection in the pad of the finger. In 1979, Johns Hopkins Hospital physician writing in the prestigious New England Journal of Medicine reported on a specific kind of felon, "Disco Felon," apparently caused by snapping ones fingers too much to disco music. Later, a correspondent to the journal suggested a better name would be "disco digit." Weird Universe quotes the following from Science Year 1982:
"A 17-year-old girl came to the emergency room complaining of an infected finger," they wrote. "Physical examination showed… a classic felon [a painful inflammation of the finger, usually near the fingernail] of the left middle finger… the patient had noticed a small crack on her finger… She thought that the crack might have resulted from snapping her fingers while she was disco dancing…"
The doctors treated the girl by draining and bandaging the inflammation. She recovered, but Walker and his associates sounded a dire warning to other disco dancers and their doctors. "Disco dancing may eventually be shown to damage a variety of body systems: namely visual, auditory, orthopedic, and nutritional. [Nutritional] damage might result from self-imposed starvation in an attempt… to wear the latest outfits."