Iodhadh is the Irish name of the twenty-fifth letter of the Ogham alphabet, ᚔ. In Old Irish, the letter name was idad. Its phonetic value is [i].
The original meaning of the letter name is unknown, but it is likely influenced by edad, much like Gothic pairþra, qairþra, together with which it forms the coda of the briatharogaim.
"Iodhadh" is also known by other names such as "Ioho", "Idad" and "Idho". Though there is never any mention of which is the correct name.
The "arboreal" glossators assign ibhar "yew".
References
Iodhadh Wikipedia(Text) CC BY-SA