Sinbad, the Thirteenth Voyage — R.A. Lafferty

As Harun lay dying here on Kentauron Mikron, all untimely still in his golden youth, he whispered a word to me that he would use if he were born again. It is the meaningless but numerologically magic word "Bangdad." It has since become the name of one of those mirage cities, one of those cloud cities, that travelers sometimes report seeing. I have learned today that its meaning in Old Kentauron is "The Last City Built by Magic."