This is not meant to be a definitive on the topic, but rather some random thoughts that I pose for people to think about when thinking of the Ogham. It is my thought that the Ogham and the Celtic tree alphabet though similar, are different from each other.

Could it be possible that it was created by Irish scholars or Druids for political, military or religious reasons to provide a secret means of communication in opposition to the authorities of Roman Britain. The Roman Empire, which then ruled over neighbouring Britain, represented a very real threat of invasion to Ireland, which may have acted as a spur to the creation of the alphabet. Alternatively, in later centuries when the threat of invasion had receded and the Irish were themselves invading the western parts of Britain, the desire to keep communications secret from Romans or Romanised Britons would still have provided…