From Alan James – 4 May 2020
Another nice possibility might be Sc and Ir G claig(e) ‘hollow, dimple’ (same in the plural), maybe orphaned from some earlier Gaelic generic, e.g. *clachan nan claige,
‘stones with the dimples’. I’ve not found a Mx cognate, though cleigh ‘hedge’ is from a verb meaning ‘dig’ (cf. ‘dyke’), so there might have been be a same-sounding verbal noun meaning ‘hole’.
Adrian Room gives Claig as the Irish form for Clegg, Co. Galway, and there is (or was) a Claig castle on Islay, but even more interesting, though frustrating, is Cleagh townland in Clonmany, Donegal, alas neither McKay nor the Flanagans give us any lead on that.