The origins of the McCullochs is shrouded in mystery. It is said that the McCullochs of Galloway were an ancient family known from time immemorium. They have been described alternatively as Pictish or Britons, but this may simply mean that the family was known to the region prior to the arrival of the Norse Gaels.
There are multiple origin stories for the McCulloch name, or names. Does the name derive from mac Cullaich (son of the boar), mac con Ulaidh (son of the dog of Ulster), mac Lulach (son of Scottish King Lulach), or mac Gwallog (son of the 6th century Briton chieftain named Gwallog)? Common modern spellings like McCulloch and McCullough are semi-standardized versions of names that have been in use for hundreds of years. The variety of spellings over this time is delightfully absurd.
It’s entirely possible that the McCulloch/McCullough names have multiple origins. The limited sample of Y DNA results available at the McCollough Project at Family Tree DNA seem to bear this out. The primary haplogroups within this project appear to be I2a2b or I-M223 (Celtic Gael); R1b or R-DF27 (Protoceltic); R1b, R-A7699 (Irish Type II, southern Ireland); or R1a, R-M198, R-BY32021 (Corded Ware). Members of these four distinct haplogroups would not have any common modern paternal ancestors. The simplest explanation is that, after the arrival of the Normans, the distinct genetic groups adopted surnames that coincidentally sounded similar and were merged later into common modern spellings. Alternatively, these distinct genetic lines might have adopted the same or similar surname in honor of the same chieftain who in near or distant memory was significant to these families.
As more McCulloch and McCullough males take Y DNA tests there will be better data to analyze. Better genetic data, and further study of the available historic and genealogical resources, may eventually lead us to a better understanding of our McCulloch origins. To learn more about Y DNA testing, visit Family Tree DNA.