It seems generally agreed that George Buchanan (1506-1582), historian, humanist scholar and the most profound intellectual sixteenth century Scotland produced [Keith Brown] was the originator of an error that persists to this day. As “a rigid disciplinarian” [Gordon Donaldson 1978] and tutor to both Mary Queen of Scots and her son, the future King James VI, he should have known better.
In a passage in ‘Polyhistor’ written probably in the 3rd C, the Roman author Gaius Julius Solinus described ‘Thule’ as ‘fruitful’ i.e. pomona after Pomona, the goddess of fruit and fruit trees, [full text below]; whereas Buchanan misconstrued the passage as meaning ‘Thule’ was large and ‘Pomona’, a separate place, was rich and fertile. Idiot! The actual ’howler‘ is in Latin, in Buchanan's ‘Rerum Scoticarum Historia’ . However, I am certain that the name [Pomona] is not to be found in any book previous to Fordun's ‘Scoti-chronicon’, 1. ii. c. 2. where he calls the Orkneys “insulae Pomoniae”. ‘Scotichronicon’ was begun in 1440 and completed 1447 by Bower. The early parts are based on Fordun's ‘Chronica Gentis Scotorum’ of c. 1360. So it may be that not all the opprobrium should be heaped on Buchanan.
Arthur Golding got it right in his 1587 translation of Solinus' ‘Polyhistor’: From the Orcades unto Thule is fyve dayes and fyve nights sayling. But Thule is plentiful in store of fruits that will last. Note that Golding's translation came only five years after Buchanan's ‘Rerum’ but seemingly the damage by then was irrevocable. And the cartographers were no help but more of them in a wee.
In a manuscript on vellum in the Bodleian (MS. Bodl. Auctar. T. ii. 28) Solinus' original passage appears: Ab orchadibus Thylen usque quinque dierum et quinque noctium nauigatio est. Sed thyle larga et diutina pomona copiosa. (MS. Bodl. Auctar. T. ii. 28) (Fol. 20b.) Early 15th C printed editions have considerable variations e.g; Ab orchadibus thylen usque v. dierum et v. noctium nauigatio est. Sed thyle larga est et diutina pomorum copiosa. (Edit. Venetiis, per Nic. Jenson, M.CCCC.LXXIII, folio.) compared with Ab arcadibus thilen usque quinque dierum ac noctium navigatio est. Sed thile larga et diutina: pynoma copiosa est. (Edit. Venetiis, anno Domini M.OCCC.LXXXXIII. die. xiii. Januariis, 4to.) Modern writers generally quote Solinus thus: Ab Orcadibus Thyle usque quinque dierum ac noctium navigatio est. Sed Thyle larga et diutina pomona copiosa est.
Early map makers such as Blaeu , Adair , and Moll  as well as Mercator and Hogg all helped perpetuate Buchanan's mislear as did Murdoch Mackenzie in 1750 when, in the first accurate survey of Orkney, he compounded Buchanan's maxie on his maps by frequently, though not invariably, giving Pomona as an alternative name for Mainland as did Thomson on his map . The Ordinance Survey [1887/8] got it right by eschewing Pomona; Bartholomew, as late as 1912 in the Survey Atlas of Scotland got it wrong by unfailingly repeating the Pomona gaff; but by ca. 1952 Bartholomew seemed to be having second thoughts by ducking the issue entirely and giving no name at all to Orkney's largest island. Come 1978 they had seen the error of their ways; dropping Pomona from their maps they asserted Mainland was Mainland - as indeed it also is in Shetland.
It was in the 19th C. that an English scholar, Sir George Webbe Dasent, the first translator of the Orkneyinga Saga, suggested that ...‘Pomona’ should be banished from the geography of the Orkneys. Even Mainland is a corruption of the Old Norse Meginland. It is not known what Mainland or even Orkney was called by the Pictish inhabitants before the Vikings arrived, and indeed no Pictish names survive anywhere in Orkney, leading some to believe that the Picts were anihilated by the Vikings. There is no archaeological evidence for this, and some evidence to the contrary, but all the old place names in Orkney are indubitably Norse. The original Viking name for Mainland was, and should be, Hrossey - Horse Isle. However, don't let any of this put you off a pint in the Pomona Inn, Finstown or a pie in the Pomona Café, Kirkwall.
As it happens, there is a family connection
with the name Pomona. Below is a transcript of p. 36 from Sail
Ships of Orkney by Sinclair Ross [W.R.Mackintosh, Kirkwall,
May 1954] The illustration is from the same page. The
picture shows the schooner Pomona discharging
cargo at the “clipper's” berth, Kirkwall.
A wooden vessel of 84 registered tons, she was built at Stromness in 1876 for Samuel Reid and others of Kirkwall. In 1886 she was purchased by Linklater of Leith and was one of the last Kirkwall sailing clippers. In the closing decade of last century the sailing clippers were replaced by steamships on time charter; the first to be so employed was s.s. Keelrow.
The Pomona was sold to Moray Firth owners and in the early years of this century she was wrecked near Fraserburgh.
Other sailing clippers of Kirkwall were: George Canning, Sir Joseph Banks,
Mary Balfour, Pandora, Paragon (old and new), and Queen of the Isles.
This all ties in with such dates as I have for James Stevens Linklater of Commercial Wharf, Leith. He was born at Aith in Sandwick on the 25th October 1850, left Orkney probably in the 1870s and set up in business as a ‘provisions merhcant’ in Leith where he died young on 21st August 1899. Presumably his death precipitated the sale of the vessel. For more about him see James Stevens Linklater. There is much more to discover about him I'm sure, but he requires a sojourn in Edinburgh. Watch this space.