This refers to a largely inaccessible area in northern Iraq bordering Turkey through which the Greater Zab River flows from Turkey through the area of the Kurdistan Regional Government (KRG) south into the Tigris River south of Mosul. The area has long been home to Kurdistan Workers Party (PKK) fighters who use it as a jumping-off point for attacks against Turkey. In its military incursion of February 2008 (Operation Gunes, or Sun), Turkish soldiers briefly occupied part of the region.
Historical Dictionary of the Kurds. Michael M. Gunter.