Is the surname Rhatigan Gaelic

Rhatigan Rattigan etc are all forms of o reachtagain. This an old family name which is mentioned in the Book of Kells. The root of the name is "reacht" which means "law" in English as the original family was involved in ecclesiatical law. The name is Irish and is found mostly in the midlands od Ireland, in the counties of Westmeath and Longfort. In the 19th century many members of this clan went to Argentina to escape the Famine and build a better life.