The explanation to your question is within the name itself, as is the opinion regarding accuracy of description. These Middle Eastern empires were known for their use of gunpowder, a new development at the time. To create and then maintain empires, these groups obviously required exceptional military forces. Thus, their inclusion of gunpowder in firearms, cannons, and so forth, was a driving factor in the expansion of these empires. There was also a great need for leadership which could acquire and distribute gunpowder, so their administrations became adept at such tasks. To put it succinctly:
"Exerting control over hundreds of millions of subjects and a myriad of diverse communities, the empires expanded their territories and power through skilful employment of gunpowder weapons and technologies..."
As no one else possessed such technology at this time, it was relatively simple for the empires to grow; eventually the development was passed on into Europe. The name is apt and accurate for these reasons.