The Ogham script recorded the earliest Old Irish texts dating between the 3rd and the 6th century CE. Ogham inscriptions are found exclusively in Ireland, Scotland, and Wales. Mostly they are genealogical inscriptions in the form of “X son of Y” on corners of large stone slabs. After the 6th century CE, Old Irish was written with the Roman alphabet, and Ogham disappeared from general but the knowledge must have been preserved in some form because our knowledge of Ogham comes from the chapter Auraicept na n-Éces in the 15th-century work The Book of Ballymote (Leabhar Bhaile an Mhóta), which also contains geneologies, mythologies, and histories of Ireland.
Various opinions exist on the exact origin of ogham. Some claim that it stemmed from a cryptic way of writing runes, some say that it was inspired from the Roman alphabet, and yet others hold that it was independently invented.
The Ogham letters are divided into four groups, each containing five letters. This yields a total of 20 Ogham letters.
When inscribed on stones, Ogham is written vertically from bottom to top. The following chart lists all Ogham letters in their vertical forms, along with their Old Irish names and meanings.
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