Different spellings that were found include Callaghan, Callahan, O'Callaghan, O'Callahan, Calahan, Cellaghan, Kalahan, Kallaghan, Kallahan, O'Kallaghan, Kellaghan, Kelleghan, Kellahan, Kelahan, Ceilahan, Ceilaghan, Callachan, Calachan, Callagan, Calagan, Kelagan, Callighan and many more.