I have just checked Ancestry.com for their free database of "Ireland Gazetteer and Surname Guide" (listings beginning of 19th century) and found no listings for the surname FERGUS. Another resource checked! And for those of you who wish to check on any other names - search this database: http://www.ancestry.com/ancestry/search/3856.htm free for ten days. Cynthia Platt, Lyman. Gazetteer of Ireland. Orem, UT: Ancestry, Inc., 1999. Platt, Lyman. Irish Surname Guide Orem, UT: Ancestry, Inc., 1999.