The McMullen name has appeared in a variety of documents, spelled many different ways. Name variations were extremely common in medieval names, since scribes from that era recorded names according to sound rather than a standard set of rules.
The names MacMillan, MacMullan, MacMullen, McMullen, McMullin, McMullan, McMillan, MacMullin are but a few of the many variations.

McMullens are first found in Agyllshire where they were seated from early times and their first records appeared on the early census rolls taken by the early Kings of Britain to determine the rate of taxation of their subjects.