1890, "mountain-forming, the formation of mountains," from French orogénie; see oro- + -geny. In reference to particular mountain-building geological periods, by 1914. Related: Orogenic (1886); orogenesis (1886).
ornithology
ornithomancy
ornithopod
ornithopter
oro-
orogeny
orotund
orphan
orphanage
Orphic
orpiment