Ogam: A form of writing in which the letters are represented by combinations of parallel strokes in number from one to five, set in varied positions along a central stemline. It was originally intended for inscription upon upright pillar stones. The alphabet consists of twenty letters and five diphthongs; the letters were incised in groups of five, perhaps indicating some relationship to finger signs.
Ogam writing may well be pre-Christian in date. It seems to be of Irish origin, flourishing in Ireland between the fifth and eighth centuries AD (Some families of monumental sculptors used it as late as the early nineteenth century.)
Macalister  states that ogam derives from the Chalcidic form of the Greek alphabet, once current in northern Italy, in Cisalpine Gaul, the Roman side of the Alps, the present provinces of Piedmont and Lombardy. He states that it was used for secret communication, being part of the signalling or gesture system of 'druidic freemasonry'. However, other authorities generally hold ogam to be based upon the Roman alphabet.
Ogam in Ireland, according to Macalister, was used for magical or cryptical purposes. 'When paganism was waning the finger signs were used as a secret language and finally used for writing epitaphs'.
Ogam is the 'occult manner of writing used by the ancient Irish', according to the Highland Society of Scotland's Dictionary of the Gaelic Language (1828).
Charles Plummeer  feels that there were uses for ogam stones other than as memorials to the dead, mentioning them as being used to show a border between two lands; the inscription on them being equivalent to a witness in determining territorial claims. O'CUrry  states that a sale of land may have been recorded in this way.
The majority of ogam-inscribed stones are found in Kerry and Cork, a 1945 survey recording 121 and 81 respectively. This would appear to indicate that west Munster was the origin of the form. In Wales there are 15 ogam stones in Pembrokeshire, introduced by the Irish during their frequent raids there in the 4th and 5th centuries. In England there are 2 in Devon and 5 in Cornwall. Raftery  states that ogam writing was transferred to south-west Wales during migrations of the Dési. Ogam characters are also found on the Isle of Man and in the north and east of Scotland. It is generally held that the Picts learned the script from the Irish settlers in Scotland.