Among his many other achievements, George Bernard Shaw, a great Irish writer and something of a wag, popularised the quaint suggestion that the humble word fish should be re-spelt as the fantastical ghoti: "gh"
The point, of course, was to draw attention to the fact that English orthography is an appalling mishmash of influences, with many rules specific to one part of the vocabulary or one part of a word, and — despite significant developments in pronunciation — not a great deal of change to the basics since the medieval period.
Though Shaw's intention was satire, from a logical point of view there is of course no reason why fish should not be spelt ghoti— which, in a roundabout way, brings us to Samuel Thomson.
Modern Scots, like Modern Irish, is a polycentrically codified language, where one spelling does for more than one pronunciation, depending on dialect. For most of the Modern Scots period, the vowel variously realised /ɑ:/, /ɔ:/ and /a(:)/ was spelt "au" initially and medially and "aw" finally. Then, as far as the Blether Region can make out, in the twentieth century, and probably after WWII, some writers of those dialects (Northern and Insular) where the sound was pronounced /a(:)/ began to suggest that it be spelt "aa" — very likely under the influence of Standard English sound-to-letter correspondences, which had led them to believe that "au" or "aw" could not be interpreted as /a(:)/.
This was not a good idea, since the reform, inspired by the mistaken belief that "au" and "aw" were not pan-dialectal forms suitable for use in a scheme of polycentric codification, actually weakened the existing polycentrism of Scots. In practice, Insular and Northern writers were much more likely to use the new digraph, while most others stuck with the "au" and "aw" familiar from the traditional literature.
Although the Northern and Insular pronunciation was also present in another peripheral dialect, Ulster Scots, at the time that was not an issue, since, as it happened, almost no one was actually writing in it. Then, in the 1990s, Ulster Scots was revived, and revived by people who were not only ignorant but had an agenda. They believed, or, more likely, affected to believe, that Ulster Scots was not Scots. Thus they adopted the "aa" digraph too, although, what with them not being linguists, their actual employment of it was somewhat inconsistent.
Readers should be in no doubt, however, that "aa" is not a part of traditional Ulster-Scots orthography, and is not used by any "rhyming weaver".
Not if one believes the BBC, however, for the corporation's website carries a grossly misleading version of Samuel Thomson's poem "To a Hedgehog", which includes the words "caad", "faan" and "aa". What Thomson actually wrote was "ca'd", "fa'n" and "a'".
In all likelihood, the work was dictated from a printed volume of his poetry and transcribed by someone influenced by contemporary revived Ulster Scots. Other websites have copied and pasted it from the BBC, including Electric Scotland, which discussesJennifer Orr's edition of Thomson's correspondence.
Frank Ferguson's mammoth anthology of Ulster-Scots writing, while a fine volume, is not the best-edited book. Although it does not make the mistake with "ca'd", etc., it prints "supercilious" in place of "superstitious". So where is one to go if one wishes to quote Thomson's poem correctly?
Well, for many writers one can turn to the Ulster-Scots Poetry Project, which carries facsimile scans of the Ulster-Scots poets, but that's hardly an answer to the problem of other folk cutting and pasting faulty transcriptions in a game of digital Chinese whispers. What needs to be done, of course, is for some Ulster-Scots fund or other to produce properly proofed diplomatic versions of those scans, which, apart from their value to literary studies, would enable corpus linguists to study such matters as — dare one say it — traditional spelling.
In truth, linguists have already been waiting many years for those diplomatic versions. Let's hope they don't have to wait too much longer.