Eadhadh
Eadhadh is the Irish name of the nineteenth letter of the Ogham alphabet, ᚓ. In Old Irish, the letter name was Edad. Its phonetic value is [e]. The original meaning of the letter name is unknown, but it is likely an artificially altered pairing with Idad, much like Gothic "pairþra, qairþra." Interpretation. The kennings for this letter value are quite cryptic. Medieval "arboreal" glossators assign "crand fir no crithach" "'true tree' or aspen" ("Crann Creathach" in modern Irish) to this letter, though this has little to recommend it by way of either the kennings or the etymology. McManus suggests  an original value of Primitive Irish"*eburas," from the Proto-Celtic *"eburo-" probably originally meaning "rowan". This is the root of the Old Irish "ibar" which refers (with qualifications) to a number of different evergreen trees. He makes sense of the kennings for "edad" in relation to its pairing with "idad". Given "éo" as the likely Old Irish word for "yew tree" (see idad) and the variant forms of Old Irish "é/éo" "salmon", we can understand the "exchange of friends" kenning; at the time the kenning was constructed this would have been understood as a word play involving exchange of  meaning between the paired "edad" ("é/éo" salmon because of the value of the letter [e]) and "idad" ("éo" yew). Medieval glossators on "edad" also suggested a connection to the discerning 'Salmon of Wisdom'. McManus also suggests that "brother of birch" may be a kenning erroneously displaced to the penultimate of the original twenty letters, from the penultimate forfeda which had an original letter name "pín" [p] that when changed later to "ifín" necessitated the invention of peithe [p] also called "beithe bog" "soft "beithe"", hence "brother of birch". This is informed conjecture, however, and will probably not be resolved  unless a full complement of kennings from the "Con" "Culainn" tradition is ever discovered (at present their values for many of the forfeda for that tradition are unattested). It could also simply be that "beithe" is to "peithe" (a rhyming pair of ogham letters) as "edad" is to "idad," and that "edad" is brother of "beithe" for this reason. Bríatharogam. In the medieval kennings, called "Bríatharogaim" or "Word Ogham" the verses associated with "edad" are: "érgnaid fid" - "discerning tree/chap" in the "Bríatharogam" "Morann mic Moín" "commaín carat" - "exchange of friends" in the "Bríatharogam" "Mac ind Óc" "bráthair bethi" (?) - "brother  of birch (?)" in the "Bríatharogam" "Con" "Culainn".