I think JKR likes names that start with the same sound (aliteration) like Godrick Gryffindor, Rowena Ravenclaw, Salazar Slytherin, Severus Snape, Peter Pettigrew and Minerva McGonegal. Still it is posible she could have read Twisters and decided to use the name for Professor McGonegal. I thought JKR probably took the name from Roman mythology.