Editor Weisman says that by calling Pakistan an acronym, Moynihan is referring to its name devised by its founders as an agglomeration of Punjab, Afghania, Kashmir, Sindh and Baluchistan.
Pakistan was named as it means Land of the Pure. Pakistan was not created as an acronym. This is a myth - note that there is no B in the name. Had it been an acronym, there would be a B for Bengal (today's Bangladesh).