The story
US, 1930s; genericized trademark for DuPont brand of polychloroprene. neo- (“new”) + isoprene (dropping the iso-), the latter from terpene. Originally called duprene (blend of DuPont and isoprene); the “new” is because neoprene was the first mass-produced general-purpose synthetic rubber.
Etymology from Wiktionary, CC BY-SA 4.0.