... the rhyme-words were merely related: l, r, n, ng, m, dh, gh, bh, mh, ch, th, f could rime together just as could gg, dd, bb. Soon the poets did not limit themselves to end-rhymes, which ran the risk of becoming monotonous, but introduced also internal rhyme, which set up what we may call a continuous ... — The Glories of Ireland • Edited by Joseph Dunn and P.J. Lennox