Part 37 of The Metrical Dindshenchas

SRUTHAR MATHA

Sruthar Matha, praise it among yourselves, O joyous people, that love it well! if ye know in full the story of the death of Matha son of Roiriu.
From Leinster of the bloody conflicts to his death in a neighbour land Matha's errand brought him, to the stream's outlet: the occasion thereof is known to us.
A wood rich in nut-clusters have I heard of in the western part of Mag Macha; there was no forest to match it for fame and for fragrance.
Such an odour rose from the wood, on the side where it moved with the wind, that no hiding-place from its fragrance was found in Banba.
Every swine that snuffed up the odour of the vast forest, their hearts would break forthwith if they could not reach the forest.
The herd of Catháir Mór, lord of horsemen, fares forth after the goodly odour: it was no prosperous enterprise for the tall slow-foot man, Matha, to be sent to master them perforce.

Neither swerve nor turn in their road could Matha get from the mighty herd: in such plight he reached Commar: promptly came his doom.
His head split, a doomed man's stroke, with the pursuit and burning heat: sadly he sinks beneath the smooth stream—small blame to him—to seek coolness.
The son of Roiriu son of fierce Rogan, chief herdsman of Cathair of Conluan, perished by his violent effort and was drowned in the river.
Therefore said every one truthfully, ‘The stream has gone over Matha—a dreadful deed!’ his name shall remain for ever to call the stream by, that it be Matha's River: it shall be a deed of note.
Before the days of Roiriu's son, cunning in casts, Sruth Nencha (though the school mention it not) was of old the river's name: I have found the great tale, above all lore.