From Prospect Magazine:
Gerin oil (or Geriniol to give it its scientific name) is a powerful drug which acts directly on the central nervous system to produce a range of characteristic symptoms, often of an antisocial or self- damaging nature. If administered chronically in childhood, Gerin oil can permanently modify the brain to produce adult disorders, including dangerous delusions which have proved very hard to treat. The four doomed flights of 11th September were, in a very real sense, Gerin oil trips: all 19 of the hijackers were high on the drug at the time. Historically, Geriniol intoxication was responsible for atrocities such as the Salem witch hunts and the massacres of native South Americans by conquistadores. Gerin oil fuelled most of the wars of the European middle ages and, in more recent times, the carnage that attended the partitioning of the Indian subcontinent and, on a smaller scale, Ireland.
More here.