... In Welsh myths we meet with Rhwddlwan Gawr, the red bony giant, and in Merddyn's time we come upon Rhydderch Hoel, or the liberal, the champion of the Christian faith, who was the friend of St. Columba, restored St. Kentigern to Glasgow, and was promised by the former that he should never fall into the hands of his enemies, but should die with his head on his pillow—a promise that a Saxon long after would have scorned.  He was a discourager of Druidism, and is reviled by Merlin.  His name may come from rhydez, the exalted... (History of Christian Names, Yonge, 1884)