The Amra Choluim Chilli of Dallan Forgaill (from Lebor na hUidre)

Decapitation original: "dichned" is the stealing of the end from a word without putting anything else in its place, as the poet said:

A meeting I shared—great the folly—
In the cold dwelling above the Ridge:
O my Lord, O King of noble mysteries original: "rí rú rá",
[unclear]...

"Rú rá"—that is the example there: for it was intended to be "rún rán" meaning "noble mystery". Double-heading original: "dochned", however, is when it has its own head ending and another head as well; and its proper form would be the doubling of the final letter of the word, as one might make "benn" peak/horn out of the word "ben," as it is said:

The desire of a man of battle is purple spoils;
He goes for God's sake, certainly not sparingly;
He placed a firm grip original: "tend" on a spear-shaft of pine;
A head is usually in the claw of Cú Echtga.

It might be that the example here refers to a physical thing—that is, that man's own head on him and someone else's head in his hand; however, these poetic devices are observed in speech and not in physical objects. Perhaps the example here is "not sparingly" original: "ní tercda", because "da" was added to the correct word: however, that is criticized, because the addition of a syllable is not "double-heading" according to its proper definition, but is rather "poetic augmentation" original: "formolad filed"; and this is the example of that:

A path from lakes to a pool of drinking
With bells of fame that is not small:
Going before horses at the end of the territory—
Good is the life in which they are there original: "annón".

What then is the "double-heading" in the verse we mentioned, "The desire of a man etc."? The answer is: making "tenn" firm/strong out of the word "ten" (meaning fire), so that it might rhyme with "chenn" head: and that is "double-heading" according to its proper definition. However, these categories are illustrated in other books in this way: "decapitation" is like "do-churin" they put, that is, the stealing of its head—the "et"—for it was "do-cuirinet" originally. "Double-heading," however, is as in "maelán," where "án" is the other head. "Metathesis" original: "cenonacnop" is as in "renchap," for it was "fenchar" originally. These examples have been criticized: the loss of a syllable is not "decapitation" according to its proper definition, nor is "double-heading" [defined by] the addition of whatever you please. There is another matter then...