I found this concept pretty interesting. Mac might not actually be a person, but someone's essence, or spirit.
The Old Norse believed that the Vörđr was a warden spirit that followed them everywhere from their birth to their death.
Vörđr, or in Old Norse vǫrđr (pl. varđir or verđir), means: “warden,” “watcher,” or “caretaker.”
In The Poetic Edda: Grímnismál, when Odin was disguised as Grimnir, he mentioned his ravens Huginn and Munin and how he feared them not returning back to him one day.
"I fear for Hugin, that he come not back,
yet more anxious am I for Munin."
(-Odin disguised as Grimnir)
Odin feared losing his mind (munin or munr) and spirit/soul (hugin or hugr), also defined as his mind and memory.
Also:
The warden could arrive before the actual person...
So in theory Mac could be older than Harry, but be Harry's spirit arriving before Harry was born. I'm not saying it's Harry. If anything Mac could be a part of Odin. The thing that stands out is Mac being called watcher which many of us have theorized about but I don't recall watcher used in this way on the forums. So just another avenue for people to investigate if they feel like it :-p
