From Juan Kodhere:

My paternal great grandfather Watterson was married to a Qualtrough (my great grandmother).
Re the erosion of Mac into C, Q or K, I don't think it was anything more than phonetic attrition especially when the language supporting these names was gradually loosing its grip to English and written records in it would not have been particularly prevalent. Given the likely elision of the Mac element of the Mac names in spoken style, it does not seem surpising to me that , like in all spoken variants of languages, there developed differences which when recorded in writing in the context of names (being, with respect to manx gaelic, the only necessary recordings in a non written language for land tenure purposes) represented the pronunciation of the people declining their identity to officials (most likely no longer galelic speakers). In fact, to illustrate this point, the elided pronunciation of manx names was actually like in Juan y Kodhere where the "y" element perhaps represented the phonetic stump of Mac thus becoming in pronunciation "urk".
Well, it's a suggestion, anyway.
Tarah for now,
slane lhiats,
Juan y Kodhere.