Ogham is an ancient 20-letter alphabet that was used for writing in Irish more than a thousand years ago.
Although Ogham died out in the 7th century, it holds a lot of cultural importance as Ireland's earliest form of writing. The alphabet's 20 characters, based on lines and dashes, were carved into stone. You can still see some ancient Irish monuments with ogham inscriptions listing the names of families. Experts disagree on the etymology of ogham, but one theory says it's rooted in the Irish og-úaim, "point-seam," or "seam made by the point of a sharp weapon."