It is from the trees of the forest that names were given to the Ogham letters metaphorically. Moreover Beithe, ᚁ, is from the birch of the forest for the first letter on the path of the Ogham alphabet. Luis, ᚂ, that is rowan, or elm in the forests. Fern, ᚃ, that is, alder in the forest. Sail, ᚄ, of the Ogham, that is, willow, again, in the forest. Nin, ᚅ, of the Ogham, to wit, maw of spear, or nettles in the woods…
_Auraicept na nÉce
The Irish claim that their script - nowadays common also in Britain, even sometimes for Latin texts - was passed down to them by Ogma.
Similar to Saxon runes, the letters of the ogham alphabet are made up of straight lines and simple angles, making it ideal for being carved or scratched onto wood and stone. It’s most commonly found in Gaelicized parts of Britain (and Ireland itself), especially in areas with little Roman influence.