This practice is met with also in English poetry, both classical and popular; but of course this is quite independent of the Irish custom.
Assonance. In the modern Irish language the verse rhymes are assonantal. Assonance is the correspondence of the vowels: the consonants count for nothing. Thus fair, may, saint, blaze, there, all rhyme assonantally. As it is easy to find words that rhyme in this manner, the rhymes generally occur much oftener in Anglo-Irish verse than in pure English, in which the rhymes are what English grammarians call perfect.
Our rustic poets rhyme their English (or Irish-English) verse assonantally in imitation of their native language. For a very good example of this, see the song of Castlehyde in my 'Old Irish Music and Songs'; and it may be seen in very large numbers of our Anglo-Irish Folk-songs. I will give just one example here, a free translation of an elegy, rhyming like its original. To the ear of a person accustomed to assonance—as for instance to mine—the rhymes here are as satisfying as if they were perfect English rhymes.
You remember our neighbour MacBrady we buried last YEAR;
His death it amazed me and dazed me with sorrow and GRIEF;
From cradle to grave his name was held in ESTEEM;
For at fairs and at wakes there was no one like him for a SPREE;
And 'tis he knew the way how to make a good cag of potTHEEN.
He'd make verses in Gaelic quite aisy most plazing to READ;
And he knew how to plaze the fair maids with his soothering SPEECH.
He could clear out a fair at his aise with his ash clehalPEEN;
But ochone he's now laid in his grave in the churchyard of Keel.
