I think the concept comes from a scripture where Jesus says he will descend from heaven with a shout and the voice of the archangel and the dead in christ will rise and those who remain will meet him in the air and forever be with the Lord. I don't remember what book that is in right off hand but I think that is the main one that is used as the concept. I think there are others like Jesus saying I will come like a thief in the night and to be watching because we know not what time he comes. anyway the word Rapture per say is not in the bible but they say the concept is. Maybe they should have just said the meeting in the air.