Luis

Luis is the standard test case for how the tree scheme was built, because the tree assigned to it is almost certainly not what the name means.

The problem

The ordinary Old and Middle Irish word for rowan is caerthann. It is not luis.

Luis is much more plausibly related to lus, a herb or plant in general, or to luise, flame or radiance. Neither gives a rowan.

What the kennings say

The briatharogaim gloss the letter with phrases about the delight of the eye and the strength of cattle, readings that suit brightness or a herb far better than they suit one particular species of tree.

The rowan attribution appears in the later scholiast material, where the commentator has already committed to the principle that every letter is a tree and works out which tree each must be. Given luis, and given that a tree is required, the rowan is a reasonable guess. It remains a guess made by a medieval scholar who was reasoning from the same limited evidence available now.

Why it matters here

Because the modern divinatory meanings for this letter are built almost entirely on rowan folklore: protection, witchcraft, the tree planted by the door against harm. That folklore is real Irish and Scottish tradition about rowan trees. It simply may not have anything to do with this letter.

McManus's general finding applies: around eight of the twenty letter names are securely arboreal, and the remainder were fitted to the scheme afterwards. Luis is one of the ones that was fitted.

The entry stands, because it is what practitioners read. The chain from the letter to the meaning has a break in it, and the break should be visible.

Ogham is written along a line. On a standing stone that line is the arris, the edge where two faces of the stone meet, and the letters are cut across or beside it. In a manuscript the line is drawn.

How the letter is formed

Luis is the second letter of the first family, Aicme Beithe, so it is cut as two strokes on the first family's side of the line. On a stone read upward along the left edge those strokes fall to one side of the arris; in the horizontal layout used by the manuscripts, the same family is written below the line. Which physical side counts as which depends on how the reader is standing relative to the stone, which is why the manuscripts, working on a flat page, had to fix a convention that the stones never needed.

Position is the whole alphabet

The system encodes a letter with two facts and no more: which of the four families it belongs to, and how many strokes it has, from one to five. Twenty letters follow from four families of five. There is no separate shape to memorise for any letter, which is what makes ogham unusually easy to cut and unusually easy to read once the families are known.

The sound

Luis carries the value L. It is well attested in the surviving inscriptions, which are overwhelmingly personal names in the genitive, cut in Ireland and in the Irish-settled parts of Wales, Scotland and the Isle of Man, and dated on linguistic grounds to roughly the fourth to the sixth centuries.

The tree glosses that give this letter a rowan belong to the manuscript tradition, several centuries later than the stones, and are treated separately in this atlas.