It is commonly said that the name McCullough, like McNally, derive from the name “mac cu Uladh” or “mac con Uladh” (son of the dog of Ulster). So who was the “Hound of Ulster?”
“Cú Chulainn was the great hero of the Ulster Cycle. Champion of the Irish kingdom of Ulster, he was the son of gods, lover of fairy-queens, and enemy of many worthy foes.” According to legend and Wikipedia: “Born Sétanta, he gained his better-known name as a child, after killing Culann’s fierce guard dog in self defence and offering to take its place until a replacement could be reared. At the age of seventeen he defended Ulster single-handedly against the armies of queen Medb of Connact in the famous Tain Bo Cuailnge (“Cattle Raid of Cooley”).
So, are the McCulloughs the genetic blood of Cu Chulainn?
Probably not, seeing how Cu Chulainn was an Irish myth. On the other hand, it is plausible that the name McCullough refers to this “hound of Ulster.” It isn’t clear, however, if the surname McCullough was originally adopted to honor Cu Chulainn, or if similarly sounding Scottish name McCulloch was Gaelized as “mac cu Uladh” because it sounded like the latter name to the ear of Gaelic speakers.
Learn more about the Irish legend of Cu Chulainn here.