Ba gleith ech nDedad.

Ba gleith ech nDedad.

(was * grazing * of horses * of Ded)

It was the grazing of Ded's horses.

That is, the place was picked clean, with nothing left behind. In the tale "Airec Menman Uraird Maic Coise" the leading character, a poet, uses three metaphorical images to express how completely the enemies of Máel Milscothach pillaged and despoiled his house and lands. He explains this one by telling us that when the horses of Ded grazed at Temair Luachra they ate not just the grass but the earth and gravel beneath it. I haven't been able to locate the tale in which that particular grazing took place, but that sort of voracious grazing is attributed also to Cú Chulainn's horses in the LU Táin, and to three destructive red deer in "Acallam na Senórach".

The second image that the poet Urard mac Coise deploys is similar in style: "Ba tenga bó Goibnenn" (It was the tongue of Gobniu's cow). This cow was apparently the same sort of voracious eater as the animals mentined above.

The third vivid image does not require a mythological explanation to be understood: "Ba diglaim dergtheined" (It was a gleaning of red fire).