http://www.houseofnames.com/xq/asp.fc/qx/seaborn-family-crest.htm

The name appears to be of British origin. I have no idea why the people of Georgia were so fond of this name. My gr.gr.grandfather was yet another GA Seaborn - Seaborn Hurst.

The Dictionary of English and Welsh Surnames claims it means "the son of Sebern." It goes on to say that there weren't too many people (comparatively) with this last name in England.