Mórbhoirneach
MÓRBHOIRNEACH—X—Morvornagh, Morvernagh, Morvorny, now always Gordon; Irish 'Mórbhoirneach,' i.e., belonging to Mórbhoireann, a place-name, meaning a rocky hill or district. This was formerly a Roscommon surname, but is now found chiefly in Co. Mayo, where it is not uncommon. It is as old at least as the 16th century. I can discover no satisfactory explanation of Gordon as its English equivalent.
Alphabetical Index to Irish Surnames