The name is derived from fulvene, which has one pentagonal ring. Other examples include methylenecyclopropene (triafulvene) and heptafulvene.
Fulvenes are generally named based on the number of ring atoms. Thus methylenecyclopropene is "triafulvene", methylenecyclopentadiene is "pentafulvene", etc.[3]
^Agranat, Israel (2012), "Ground-State Versus Excited-State Polarity of Triafulvenes: A Study of Solvent Effects on Molecular Electronic Spectra", The Jerusalem Symposia on Quantum Chemistry and Biochemistry, 8: 573–583, doi:10.1007/978-94-010-1837-1_36, ISBN978-94-010-1839-5