Where does “Kjartan” come from?

Kjartan (Icelandic) comes from Old Norse Kjartan, from Old Irish Muirchertach.

Ancestry of “Kjartan”, step by step

Step	Language	Word	Meaning
1	Old Norse	Kjartan	—
2	Old Irish	Muirchertach	—

Kjartan — Etymology, Origin & Word History | Etymology Explorer