There is no K in Irish Garlic alphabet. And consonants in this case with C is pronounced like a K in Englisch. All languages in Europe that at some point adopted the Latin alphabet (incl their own new letters) have different pronunciation, like in German our C is pronounced tseh, and our I is pronounced like "ee" like see, and we have letters like ö, ä, ü and ß which are pronounced like ae, oe, ue, and a sharp ss, and the former 3 doing so using rounded lips. a and ä for example are completely different letters, if someone has the name Käthi then pronouncing it any other way is wrong and doesn't even sound the same.
I am German and learned a little bit of Irish Gaelic so I know it's alphabet and always knew Cillian himself is Irish and I know someone with the same name.