Ogham

The runes use a system called Ogham, an Irish alphabet that was abandoned in the 10th Century.

SUNK 2008

There is an ancient alphabet called Ogham, not intended for our kind of writing—this is something like that.

Greenwitch Susan Cooper 2002

There is an ancient alphabet called Ogham, not intended for our kind of writing—this is something like that.

Greenwitch Susan Cooper 2002

There is an ancient alphabet called Ogham, not intended for our kind of writing—this is something like that.

Greenwitch Susan Cooper 2002

Whether the Ogham was a native alphabet or a derivative from another, it was at first employed only to a limited extent.

Early Bardic Literature, Ireland. Standish O'Grady 1887

(For the record, I had no idea what Ogham Divination was but did a search for obscure courses.)

Dean Shareski: Personalization vs. Standardization: It's Tough To Do Both Dean Shareski 2010

Also it looks like the Ogham system is derived from the Latin alphabet, but that is beside the point though this fits the archaeology, internal structure, etc. best and this is the most widely accepted theory today.

The Volokh Conspiracy » Be Careful Relying on Ancient Sources: 2009

AFAICS, the tally mark hypothesis seems to be the most widely accepted approach to the basis of Ogham in the academic articles and books I have come across.

The Volokh Conspiracy » Be Careful Relying on Ancient Sources: 2009

Indeed, when Major Bryan first meets Donat Clare, Clare asks him to arrange for the return of a looted Ogham stone 12.

The Manuscript Man 2008

Indeed, when Major Bryan first meets Donat Clare, Clare asks him to arrange for the return of a looted Ogham stone 12.

The Little Professor: 2008