Pliny the Elder, a Roman writer, documented the earliest account pertaining to the inhabitants of the peninsula around the mid-first century AD, referring to them as the Catharrei, a designation which may have derived from the name of a prominent local settlement.[30][31] A century later, Ptolemy produced the first known map to depict the peninsula, referring to it as Catara.[31][32] The map also referenced a town named “Cadara” to the east of the peninsula.[33] The term ‘Catara’ (inhabitants, Cataraei)[34] was exclusively used until the 18th century, after which ‘Katara’ emerged as the most commonly recognised spelling.[33] Eventually, after several variations – ‘Katr’, ‘Kattar’ and ‘Guttur’ – the modern derivative Qatar was adopted as the country’s name.[35]

In Standard Arabic, the name is pronounced [ˈqɑtˤɑr], while in the local dialect it is [ˈɡitˤar].[11]

Source: Qatar – Wikipedia