Before discussing the letter names it is worth examining the compelling notion that Ogham and its link with trees may even have given the Irish their name in their own language. The Irish and Welsh at the time of Ogham's invention spoke very similar languages and they naturally borrowed words from one another. A striking feature of this is the fact that the Irish borrowed the word gwyddel from the Welsh to describe themselves. Most Irish people today are totally unaware that the name Gael or Gaedhil stems from a Welsh source. So what does gwyddel mean? Most scholars believe that it comes either from gwydd meaning 'wild' or gwydd meaning 'wood/forest. A gwyddel then is either a wild man or a man from the woods, neither of which is very complimentary. But if gwyddel is simply a derogatory word for a wild woodsman, why did the Irish adopt it with such enthusiasm? From the sixth century on, Irish genealogists and historians promoted the term to such an extent that Érainn, the original name for the Irish, almost became extinct?
The answer lies in looking at the meanings of other words in Welsh that derive from gwydd. Among them are gwyddon 'scholar/scientist and gwyddoniaeth 'science/knowledge'. Most interesting of all, however, is gwyddor 'rudiment/ element', or more specifically, 'alphabet' (the alphabet in Welsh is called Yr Wyddor). This last meaning is identical to that of the related Irish word fid which also means both 'wood' and 'letter'. Gwydd in Welsh thus seems to combine the meanings of the Irish words fios (wisdom or knowledge) and fid. In other words, far from gwyddel meaning a wild man of the woods, it in fact means something like 'one who has knowledge of tree-letters and is a reference to the use of the tree alphabet Ogham by the Irish. This must have been taken by them as a compliment to their learning and the name gwyddeleg adopted to describe the standardised Irish of the scholars, which was informed by the rules of grammar. Auraicept na nEces or the Scholar's Primer, is quite explicit that gaedelg (or gwyddeleg) is the 'selected language' of the scholars and that its invention coincided with the invention of the Beithluisnin or Ogham.