The actual origins of Ogham are often debated by scholars.
The appearance of Ogham stones seems to coincide with the introduction of Christianity to Ireland.
Pagan practices used by Christians
However, when the Early Christians arrived in the 4th Century, it was the church’s policy to adopt pagan practices and convert them to Christian use.
Many Ogham scholars believe there is phonological evidence to suggest that the Ogham alphabet is part of an older Druid language, perhaps dating back to the first century BC and brought into the mainstream by the Christian monks who ordained many druids into the Christian faith.
Why was Ogham invented
The reason for the invention of the Ogham is also debated. Some believe it was created by the druids as a secret language that enabled them to communicate without the Romanised British understanding.
Another idea is that Christians in Ireland invented the alphabet out of the desire to have a unique set of letters to write in old Irish which was difficult to translate into the Latin alphabet.
The Book of Ballymote, which recorded the mythologies and culture of the Celts also recorded the Ogham. As well as Ogham, the Book of Ballymote contained Christian teachings and governmental records of the time such as taxes and rules for measures of Irish versification.
In here they were written horizontally rather than from bottom to top as they appear on the stones. Books similar to the Ogam Tract were used to teach Gaelic poets who learnt 150 varieties of Ogham alphabets during their study.
The reason for this is disputed but largely thought to be a way of training the brain to think in different grammatical styles, codes and concepts.