The story
Contraction of penta-hexa-hepta-graphene, penta- + hexa- + hepta- + graphene from the ring structures of phagraphene, having five-, six-, and seven-sided rings in the macromolecular structure.
Etymology from Wiktionary, CC BY-SA 4.0.
phagraphene
Today it means: A two-dimensional form of graphene, the allotrope of carbon found in graphite, with 5/6/7-sided rings instead of just the 6-sided ones found in conventional graphene. Full definition →