Around the middle of the second century CE, the satirist Lucian of Samosata says he saw a painting in southern Gaul that puzzled him. It showed Heracles — recognisable by the lion skin, club and bow — but as an old man, bald in front, with the rest of his hair grey, skin burnt dark. From the tip of his tongue ran fine chains of gold and amber, and by them he was towing a crowd of men, whose ears the chains were fastened to. The men were not resisting. They were following happily, and could easily have got free.
A Gaul standing nearby explained it. Among his people, he said, eloquence is Heracles rather than Hermes, because Heracles achieved everything by force and eloquence is the strength of the old; and the ears of the persuaded are fastened to the speaker's tongue. The god in the picture, he told Lucian, was called Ogmios.
It is the single best surviving account of what a Celtic-speaking person thought about anything, and it survives because a Greek writer found the image odd enough to record.
How far the Ogmios–Ogma equation can be pushed
Not as far as most sources push it. The Gaulish Ogmios is attested by Lucian's account and by two lead curse tablets from Bregenz in Austria which invoke him — so he existed, was worshipped, and was known across a wide area of the Continent.
The Irish Ogma is a champion of the Tuatha Dé Danann, called grianainech, "sun-faced" or "of the shining countenance", and trénfher, strongman. In the second battle of Mag Tuired he is the one who hurls the enormous flagstone that Lugh then matches, and he recovers Tethra's sword from the Fomorian camp — a sword which, when drawn from its sheath, recounts everything it has done.
The names look alike and both figures combine strength with words. But the sound correspondence between Gaulish Ogmios and Irish Ogma is not regular, which is a real problem: names that descend from a common ancestor normally change in predictable ways, and these do not. Explanations offered include a borrowing rather than an inheritance, or an unrelated Irish name that attracted the Gaulish figure's attributes. It is a comparison worth making, clearly labelled as unresolved rather than asserted as fact.
Who invented ogham, according to the people who used it
In Lebor Ogaim, the Ogam Tract, states its origin plainly: ogham was invented by Ogma, a man well skilled in speech and poetry, and its purpose was to be a script for the learned, obscure to rustics and herdsmen. The first thing ever written in it was a warning — seven letters b cut on a birch and sent to Lugh, meaning that his wife would be carried off to the otherworld seven times unless birch protected her.
That aetiology tells us two things. Medieval Irish scholars regarded the alphabet as a professional cipher belonging to the learned class, and they attributed it to the god of eloquence rather than to a king or a saint. Whether either belief has any bearing on how the script was actually devised is another question.
The script itself is real archaeology
Ogham is not a mystical tradition; it is a writing system with roughly four hundred surviving stone inscriptions. The distribution is concentrated in the south-west of Ireland, especially Kerry, Cork and Waterford, with a substantial group in Wales — often bilingual with Latin — plus examples on the Isle of Man, in Devon and Cornwall, and in Scotland where a later Pictish tradition uses it.
The letters are strokes and notches cut across or along the arris, the edge of the stone, read from the bottom up. Almost all the inscriptions are short and formulaic: a personal name in the genitive, with a father's or ancestor's name. They date mostly from the fourth to the sixth centuries CE, which makes them the earliest written Irish we have and a major source for the language before Old Irish.
The design of the system implies contact with Latin grammatical thought — the letter inventory and its ordering look like the work of someone who had thought about how an alphabet is structured — while the physical form, cut on an edge with no ink and no curves, is entirely its own.
The tree calendar is not ancient, and it is not a calendar
Each ogham letter has a traditional name, and a number of those names are tree names: beith birch, dair oak, coll hazel. Medieval glossaries also list kennings for the letters, and later grammatical tradition elaborated the arboreal scheme considerably.
From this Robert Graves, in The White Goddess in 1948, constructed a thirteen-month "Celtic tree calendar" assigning a tree to each lunar month, together with a system of correspondences and a seasonal mythology. It has since appeared in an enormous number of books, greeting cards, jewellery ranges and websites, usually described as ancient Druidic lore.
It is not. Graves invented it. No medieval Irish source arranges the letters into a calendar, no Irish year had thirteen months of that kind, and the tree associations of the letters are partial rather than systematic. The related practice of casting ogham staves for divination is likewise a modern reconstruction — an attractive one, well established in contemporary Druidry, with no medieval evidence for it. Anyone selling an "ancient Celtic tree horoscope" is selling a twentieth-century English poet's idea. On how such systems acquire the appearance of antiquity, symbol traditions is the wider survey.
Ogma's own story ends abruptly
He is given a wife, Étan, and sons, and in some accounts he dies at the second battle, killed by the Fomorian king Indech — though the same text elsewhere has him alive afterwards, which is normal for this literature. What he does not have is a cult site, a festival, or a body of tales of his own. He is a strong man in a battle narrative and a name in an alphabet's origin story, and the eloquence that makes him interesting is documented in Gaul rather than in Ireland.
Why would an alphabet need to be hidden from rustics?
Because literacy was professional property. Early Irish law and learning were controlled by hereditary learned families with a strong interest in their skills being non-obvious, and a script that requires you to know the class-and-stroke system is a modest but real barrier. Whether ogham was genuinely used as a cipher, or whether the tract is dressing up a functional monument script as an arcanum, cannot be settled — but the inscriptions themselves are boundary markers and memorials, which are public objects, so the secrecy claim sits oddly with the archaeology.
Can ogham write modern English?
Only awkwardly, and this matters because ogham tattoos and jewellery are now common. The system was designed for the sound inventory of Primitive Irish, has no letters for several English sounds, and includes letters for sounds English does not use. The supplementary letters, the forfeda, were added late and are irregular. Transliterations are therefore approximations, and two different vendors will often give two different renderings of the same name.
Is the Pictish ogham the same system?
The letters are, the language is not. Scotland has around thirty ogham inscriptions, several of which cannot be read as Irish or as any other known language, and they use a somewhat different set of conventions, including a vertical stem-line drawn on the stone face rather than the natural edge. They are among the most frustrating documents in early medieval Britain: legible letter by letter, and meaningless as words.