There is a story behind it. Once Pir Mehr Ali R.A. went to his Sheikh's home & there had some sort of invitation & lot many people were there. So, in the kitchen a dog came a jumped over the flour and put his foot in that. A cook get confused what to do with that? Reported to Sheikh of Mehr Ali R.A. He said, ask Mehr Ali R.A. And Mehr Ali R.A. said make chapati for me form the part of dog foot & use the rest one for guests. After that Sheikh asked Mehr Ali R.A. what you advised them? He R.A. said I ate that. And Sheikh gave him faqeeri.