Linguistics
Ancient Ireland's alphabet was carved along the edge of standing stones
Ogham, used to write early Irish from around the 4th century AD, consists of groups of lines and notches carved across the corner edge of a stone or wooden post rather than on a flat face. Each letter was traditionally linked to a tree name, giving rise to the enduring idea of a Celtic 'tree alphabet,' though how deep that tree association really went is debated by scholars.