What is "gangani"

The Gangani were a people of ancient Ireland who are referred to in Ptolemy's 2nd century Geography as living in the south-west of the island, probably near the mouth of the River Shannon, between the Auteini to the north and the Uellabori to the south. There appears to have been a people of the same name in north-west Wales, as Ptolemy calls the Llŷn Peninsula the "promontory of the Gangani" .