The name may derive from "Qatara", believed to refer to the Qatari town of Zubara, an important trading port and town in the region in ancient times. The word "Qatara" first appeared on Ptolemy's map of the Arabian Peninsula.[citation needed]

In Standard Arabic the name is pronounced [ˈqɑtˁɑr], while in the local dialect it is [ɡitˁar].[5] In English-language broadcast media within Qatar—for example, television commercials for Qatar Airways and advertisements concerning economic development in Qatar—the name is pronounced "KA-tar", with a distinct differentiation between the syllables from the forming of the 't' sound.

Source:
Wikipedia's Qatar Page