Tinne (letter) explained

Tinne is the Irish name of the eighth letter of the Ogham alphabet, ᚈ, meaning "ingot" or "iron bar". Its phonetic value is [t].^[1]

Bríatharogam

In the medieval kennings, called Bríatharogam or Word Ogham the verses associated with Tinne are:

trian roith - "one of three parts of a wheel" in the Word Ogham of Morann mic Moín

smiur gúaile - "marrow of (char)coal" in the Word Ogham of Mac ind Óc

trian n-airm - "one of three parts of a weapon" in the Word Ogham of Culainn.^[2]

Notes and References

1. Book: McManus, Damian . A Guide to Ogam . 1991 . Maynooth Monographs . 4 . 1-870684-75-3 . 0790-8806 . An Sagart . Co. Kildare, Ireland . 37 . The kennings equate this name with the word tinne 'bar, rod of metal, ingot, mass of molten metal'. The word is probably related to Old Irish tend 'strong' or tind 'brilliant' and the value /t/ is beyond dispute..
2. [Auraicept na n-Éces]