This everyday word has undergone several changes in its history. It began life in the late 1500s as god be with you (or ye) , spelled variously as god be wy ye , god b'uy , and so on. The first part changed to good either on analogy with such other greetings as good day, good morning and good night , or as a euphemistic deformation to avoid the blasphemy of saying god (taboo avoidance) - or due to a combination of the two. The various independent words in god be with you were amalgamated into one, goodbye , and ultimately even this was shortened (clipped) to bye . (L. Campbell, historical linguistics.)
One Thousand And One Nights of Dreams:-- Come True!