Leslie Quilliam's book "surnames of the Manks" notes that "...the erosion of Mac had taken place by the beginning of the 17th century, when the recording of Baptisms, Marriages and Deaths began." I wonder if the Clergy had begun to omit the Mac prefix in their registers and if this became the norm.

I understand that there was a tendency to eliminate features that indicated a Manx or Gaelic origin and the dropping of Mac from a surname might point to a more highly thought of English origin.

A similar position was involved with speaking Manx Gaelic. In times past some parents who were bilingual took care that their children did not speak Manx. This was convenient if the parents did not wish the children to know what was being discussed but they actively discouraged their children from becoming Manx speakers. However, the effect of this was to promote the Anglicisation of the next generation and this was considered a status symbol.