The story
From methyl + cyclopentadiene.
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: Any of three isomeric cyclic diolefins, (methyl derivatives of cyclopentadiene), the organic precursor to the methylcyclopentadienyl-ligand commonly found in organometallic chemistry. Full definition →
From methyl + cyclopentadiene.
Etymology from Wiktionary, CC BY-SA 4.0.