The Nuttall Encyclopedia
n alphabet of 20 letters in use among the ancient Irish and Celts, found carved on monumental stones in Ireland, Wales, Cornwall, and the North of Scotland.
Wood, James, ed. Entry for 'Ogham'. The Nuttall Encyclopedia. https://www.studylight.org/encyclopedias/eng/nut/o/ogham.html. Frederick Warne & Co Ltd. London. 1900.