Translation according to P. W. Joyce:
Caherlissakill in Galway ; Cathair-lis-a-chuill, the caher of the lis (old fort) of hazel (coll, hazel). Here the caher either stood near an ordinary lis or was the lis itself. MacNeill's observation applies here. See p. 14 [see below].
Professor John MacNeill, in his paper on "Place-Names and Family Names" of Clare Island (p. 16) makes a very important remark, to the effect that a little group of words is sometimes taken as one combined noun, in which case the individual words, coalescing into the single compound term, cease to be regarded as in separate use, and consequently (some or all) escape inflection. This remark applies to many names, and I shall often have occasion to refer to it. A good example is Brackaghlislea, in Derry, of which the accepted Irish form is Breacach-Lis-Léith, the speckled spot (Breacach) of Lislea, where Lislea (grey lis) is the little "group". Independent of the group influence, Lis (nom. Form) would be Leasa (gen.); but it here escapes this inflection. But lea or líath is inflected to léith (gen. sing. masc.). Sometimes, as here, only one word of the group escapes inflection; sometimes more.