The earliest surviving mention of the Orkney Islands is found in the accounts of the Roman geographer Diodorus Siculus.

Writing around 56BC, Diodorous set out to record an account of, what was then, the known world.

Diodorous's account is based on a report by the Greek sailor Pytheas of Massilia, who is thought to have sailed around Britain in 325 BC.

Pytheas' account of this journey, Concerning the Ocean, has since been lost, but his work was extensively quoted from over the following centuries.

Diodorus described Britain as triangular. The three points of this triangle, he wrote, were Cantium, Belerium and, jutting out into the open sea, Orkas - a place of immense waves.

"Britain is triangular in shape, much as is Sicily, but its sides are not equal. The island stretches obliquely along the coast of Europe, and the point where it is least distant from the continent, we are told, is the promontory which men call Kantion and thus is about one hundred stades from the mainland, at the place where the sea has its outlet, whereas the second promontory, known as Belerion, is said to be a voyage of four days from the mainland, and the last, writers tell us, extends out into the open sea and is named Orkas."

This promontory, Orkas or Orcas, is generally thought to be Dunnett Head in Caithness - the most northerly point of mainland Scotland. From here, Orkney is clearly visible across the Pentland Firth.

Orcades

By the first century AD, the islands were being referred to by their Latin name "Orcades" - the maps of the Roman geographer, Pomponius Mela, being the earliest surviving record of this name.

Later, around 98 AD, the Roman writer Tacitus, while documenting the campaigns of his father-in-law, the Roman general Agricola, states that after the defeat of the Picts at the battle of Mons Graupius, Agricola despatched a force to sail around the northern tip of Britain.

This expedition, which took place around 84AD, saw the explorers experience favourable weather and return unscathed after having first "discovered and subjugated the Orcades hitherto unknown".

According to Tacitus, these islands were "beaten by a wild and open sea".

He then goes on to tell how the explorers sighted the island of Thule before being forced southwards by the onset of winter.

The position of Thule has been long debated but it is generally thought that the Roman seamen sighted Shetland. Some scholars believe Agricola actually reached and landed in Shetland.

For more on alleged Roman contact with Orkney, click here.

Ptolemy's map

Around 140 AD, the Greek geographer Ptolemy of Alexandria produced an early map of Britain. Again using earlier sources, Ptolemy named three headlands - Tarvedrum quod [est] Orcas, Viruedrum and Veruvium.

The interpretations of these named headlands vary but, regardless of opinion, it shows an early mention of Orkney being used as a reference point.

By 1541, the name "Orcades" was appearing on globes, earlier maps and charts usually having very crude representations of Scotland.

For an example of a 17th century map of Orkney, click here.

But although the Latin name continued in use on documents and maps, the islands' common name, Orkney, was in widespread use elsewhere.

For more on the Orkney placename, click here.