The surname Tully (Tuley, Tullio, Tulley, etc.) appears to be locational in origin, and is believed to be associated with the Irish and Scots, meaning "one who came from Tully (small hill)." There is a coat of arms associated with this name.
Tully can be a girls name as well! My friend's name was Petula and she was refered to as Tully. Our friend Tina-Merry called her child Tully after that particular reference.
-- Anonymous User 4/8/2007
I get this confused with Tilly, the names are very similar in spelling and pronunciation.
One of the Great Houses in A Song of Ice and Fire is Tully, Lords of Riverrun. The current head of the family is Edmure Tully. Their sigil is a springing trout on red and blue.