Here are a few comments I wrote in a book about my McGregor ancestors:
"Have you noticed a couple of different spellings of ‘McGregor/MacGregor’ already in this story? There is no ‘right’ way to spell that name. I have seen more than twenty different ways in old documents. It largely depended on the whims of the writer, usually the parish priest. For example, in Kenmore parish (‘our’ John’s parish) it was usually spelt ‘McGregor’ for men and ‘NcGregor’ for women except for the period from 1791 til 1830 when it was spelt ‘MacGregor’ for both men and women. After 1830 it reverted to ‘McGregor’ for both. (The forty-year period of the ‘MacGregor’ spelling was when a Reverend Colin MacVean was the minister of Kenmore parish.) In the neighbouring parish of Dull it was generally split between ‘McGregor’ and ‘McGrigor’."
In hundreds of hours spent poring over thousands of baptism records another thing I discovered was that native Gaelic speakers tended to use "Mc" or "M' " whereas scribes educated in England or the Scottish Lowlands tended to use "Mac". [References to 'our' John below are to my great grandfather, John McGregor (1852-1947).] Here's my reasoning:
"In our particular line, our family name was spelt ‘McGregor’ (with one exception, ‘McGrigor’) for over 200 years, dating back to the first parish records. (‘Our’ John’s father, Alexander McGregor, born during Rev. MacVean’s time as parish priest, did not have his baptism recorded, but at his marriage in 1850 it was written as ‘McGregor’.) Finally, spelling reforms at the turn of the 20th century mandated a change to ‘MacGregor’ when children went to school.
"‘Our’ John, a native Gaelic speaker, was reportedly unhappy when the spellings of his children’s names were ‘corrected’ to ‘MacGregor’. Originally ‘mc’ was an abbreviation of ‘mac’, and a son of a man named Gregor would be called ‘mac/mc/m‘Gregor’. A daughter however was ‘ncGregor’ and a grandchild was ‘mhic (or ‘vc’) Gregor’ (see Eoin Cam above). Gradually ‘nc’ and ‘mhic’ and their variants disappeared and ‘mc’ took on the additional meaning of ‘descendant’.
"To rename John’s daughter Mary ‘Mac’Gregor would have seemed wrong: Mary was a daughter of John, not a son of Gregor. But both were descendants of Gregor, so ‘Mc’Gregor or ‘M‘’Gregor’ would have made perfect sense, whereas ‘Mac’ too specifically said ‘son’.
"John signed his own name ‘Mc’ or ‘M‘’ all his life.
"However, despite having said all that, any spelling of our name is really as good as any other and, genealogically-speaking, spelling differences mean nought."
Peter