th changed to ch.
The change of th into ch seems to be universal in dachaidh, home, from do-thigh, and in gu bràth, for ever, written ‘gu brach’ in the 1408 charter. The latter is pronounced gu brách in Irish and is dy bragh in Manx. Bothan, hut; lothag, filly; triath, a chief, etc., and féith, vein, are respectively bochan, lochag, triach, and féach in Arran. Bochan, lochag, triach, and feich are all met with in Shaw’s Dictionary. Triach occurs in Kintyre, and MacAlpine pronounces triath and its adjective triathail with ch. At the end of monosyllables th is often represented by gh in MacAlpine’s pronunciation, for example, in guth, voice, dlùth, wrap, mùth, change, maoth, soft. Compare the Manx daghy, dye, our dath, and myghin, clemency, our maothainn.
In Arran a Thighearna as an exclamation may be heard as a Chiarn, and Shaw gives ‘ogchiern, a young lord’; the Manx is Hiarn, pronounced, according to Professor Rhys, Chiarn. Medially and finally th is pronounced ch in laitheil, daily, snàithean, thread, maith, good, ràith, quarter of year, ruith, run. Súith, soot, Irish súithche, Middle Irish súithe, Old Irish suidi, is here sùiche. Shaw has laichol, daily.
In Kintyre snàithean, ràith, here ‘ràiche,’ ruith, and sùith, here ‘sùich,’ have ch. In other instances in this district and also in Islay ch for th is associated with an intrusive slender vowel after long, broad vowels. Thus càth, husks of corn, is here càich; gaoth, wind, is gaoich, which occurs also at Shiskine in Arran; luath, ashes, is luaich, and sàth, repletion, is sàich.
MacAlpine usually writes such words with the slender vowel and th and pronounces ch, as in àith ‘àich’ for àth, kiln; càith ‘càich,’ husks; luaith ‘luaich,’ ashes; sàith ‘sàich,’ repletion. In some instances he gives also the usual form. Of gaoith, ‘gaoich,’ he says, ‘sometimes the nominative, and always the genitive of gaoth, wind.’ He gives this ch, with alternative pronunciations in some instances in snàithean, maith, ràith, ruith, and sùith.
