well actually, Jah, or Jah Jah is specifically referring to Haile Selassie (a late King of Ethiopia), he arrived at Jamaica, greeted by 100-200 thousand people and spoke there. Rastafarians believe that he is God, himself (Rita Marley claimed she saw scars on Selassies hand, that look liked he was crucified, she instantly converted after he spoke). Selassie on the other hand, doesn't believe it, but had shown kindness to the Jamaicans, encouraged them to help their country first and move back to Arica (they wanted to move back), he gave them (i believe) around 500 sq miles of land in Africa.