 Pytheas described Great Britain as being triangular in shape , with a northern tip called Orcas . This may have referred to Dunnet Head , from which Orkney is visible . Writing in the 1st century AD , the Roman geographer Pomponius Mela called the Orkney islands Orcades , as did Tacitus in AD 98 " Orc " is usually interpreted as a Pictish tribal name meaning " young pig " or " young boar " . The old Irish Gaelic name for the islands was Insi Orc ( " island of the pigs " ) . The ogham script on the Buckquoy spindle @-@ whorl is also cited as evidence for the pre @-@ Norse existence of Old Irish in Orkney . The Pictish association with Orkney is leant weight by the Norse name for the Pentland Firth – Pettaland @-@ fjörðr i.e " Pictland Firth . 
