Ogham is an early medieval Irish writing system in which letters are represented by groups of notches and strokes carved along the edge of a stone, most commonly used to record personal names and lineages. The Knockrour stone carries an inscription that two nineteenth and twentieth century scholars read in completely different ways, arriving at completely different words, which is itself a measure of how much uncertainty surrounds it.

The stone was found by a tenant farmer in a burial ground set within an enclosure at Knockrour, and he presented it to the Cork antiquarian John Windele, who visited the site in 1851. Richard Rolt Brash, writing in 1879, read the inscription as MUDDOSSA M(A)QQA AT, a reading consistent with the standard ogham formula recording a person's name and parentage. R. A. S. Macalister, however, examined the stone later and read it in the opposite direction entirely, arriving at FAANN MACCOLLUM, and on the basis of that analysis declared the inscription a forgery. Whether the stone was genuinely ancient and simply ambiguous, or whether someone had cut or altered the marks deliberately, was not resolved. The stone left Ireland altogether and is now held at the Pitt-Rivers Museum in Oxford, putting it well beyond casual inspection. Two further possible ogham stones have also been identified in association with the broader Knockrour site, which suggests the location had some significance in the early medieval period regardless of what is decided about the disputed example.