Sithric's nickname Carrach-in-Cairn meant he had a scabbed, mangy or bald head or rough-faced and lived in Carn, Tullyhunco townland before becoming chief.
On the death of the previous chief, his father Duarcán Mág Tighearnán, the Second in 1290, Sithric took the chieftaincy and resided in the castle of Croaghan of the Cups (Irish- Cruachan O'Cúbhrán), now in the townland of Coolnashinny, besides the modern town of Killeshandra.
Sithric died in 1290 shortly after succeeding to the chieftaincy but some of the annals give a later date.
The Annals of Ulster for 1290 state Carrach-in-cairn Mag Tigernain, chief of Tellach-Dunchadha, rested in Christ.
The Annals of Loch Cé for the year 1293/4 state- Two chieftains of Tellach-Dunchadha died in hoc anno.