While browsing online I found that some copies of the Waterford and South East Arch Journal was now online. I found this amazing quote relating to Knockgraffon Motte. I don't know how accurate his sources are and of course it could be the remains of a souterrain etc but still it is a pretty cool reference to find online.

"The remains at New Grange, near Drogheda, are considered to be tombs, and the similar mounds in the diocese of Cashel and Emly may be also. The most notable of these are two in Rathcool parish-one at Ardmayle, and one at Knockgraffon. There is no doubt that these mounds are hollow, and there is but little doubt that some day they will be destroyed. One of them had in recent years a narrow escape from a passing railway. I have been informed on good authority that some fifty years age certain workmen, while tilling the field about this latter, came on a subter-ranean passage in which they found what they described as two old swords and an old bucket, which, of course, they treated as rubbish."