From Alan James – 6 May 2020
I think Cleich helps a bit, though I’m afraid mainly i na negative way. -ch came to be used increasingly in the past century in preference to the -gh generally used in Irish-English spellings, for the aspirated consonant that is the familiar, strongly sounded Scots ‘ch’, but in Irish tends to be weakened and lightly voiced [j], or lost altogether. In Manx, -gh was (according to George Broderick) closer to the Scottish sound. The variation between Cleagh and Cleich leaves it unclear whether the consonant in Gaelic was velar (‘broad’) or palatal (‘slender’), the distinction would have been lost in Scots speech. I think Cleich makes cliathach ‘sloping’ doubtful, it would hardly be the reflex of disyllabic [i-a] , and anyway doesn’t really really suit the field. And –ch makes clais ‘trench’ (as in the neighbouring field, The Clash), cliath ‘hurdle’, claig ‘hollow, dimple’, or cla(i)dh ‘digging’, also ‘grave, graveyard’, all less likely. Manx cleigh ‘hedge, stone dyke, fence’ looks closest to Cleich, but I’m not sure (pace Broderick) whether the -gh in that word is for [x], as it’s the equivalent of Sc G cla(i)dh, and Cregeen recorded Cleiy as an alternative. Some connection with clach, ‘stone’, would make sense, but I can’t see how Cleich can be a form, variant or relative of that word in Scottish, Irish or Manx Gaelic.
So I think it remains a mystery.
Mike may have other ideas!