R Surname for Northern Ireland

I am looking for Riddell descendants. It is claimed by a few authors that the family was from Ballymeath. I have searched several Northern Irish references and found no such place. The claim was put forth by GT Ridlon in a book about the Riddell family. I have read the book written by William Pitt Riddell and Edited by John Leonard Riddell on the Riddell and I am more inclined to believe their claim due the fact that both these authors were doctors and chemists and exacting in finding information. Also, these Riddell brothers were closer in time to the events then Ridlon is. As a result, I concur with the Riddell brothers assessment that the Riddell family in which I and they were related are from Coleraine, Londonderry, Northern Ireland. Also as a pattern, the Scots Irish on the 1600s tended to go to Londonderry County, New Hampshire (aka Nutfield) and then many went on to other Scots Irish settlements like Coleraine, Massachusetts. As was the case with my branch of Riddells when they came to America.