The Cambridge Guide to Australian English Usage - Noel's ESL ...

M
Mac or Mc How do you write the name of a well-known hamburger restaurant
chain?
McDonald’s MacDonald’s Macdonald’s
The first spelling is the one used by the company, although the second or third
spellings are also used by many people with the same surname—as a glance at the
metropolitan phone book will confirm. Apart from those three spellings, there are
two other ways of writing Celtic surnames of this kind: Mcdonald (which is rare
by comparison with the other three above); and M’Donald, used in the nineteenth
century, and still to be seen in the names of Walter Scott’s characters, and sometimes
in references to M’Naghten rules (a legal plea which seeks to defend someone on
the basis of diminished responsibility).
Ultimately, the decision about how to spell these surnames rests with the
individual. Individual choices can put both Mc and Mac in the same sign, as in
McCulloughs of Macquarie. Yet there are some general trends towards one or the
other spelling, in that Irish surnames seem to stay with Mc, asinMcConnochie,
McElroy and McEvoy; while Scottish names more often convert to Mac (with
or without a following capital). It means that Scottish names are around in two
or three forms: McDonald/MacDonald/Macdonald. Other things being equal, the
commoner the name, the more chance of it having the Mac forms. And mac is the
spelling found in common words derived from Mc surnames, such as macadamia
(nut), with no capital letters. (See further under capitals and also eponyms.) In
mackintosh “raincoat” the spelling adjustments have gone one stage further, with
the insertion of the k to conform with standard c/ck rules. Compare the alternative
forms of the original surname: Mclntosh/MacIntosh/Macintosh.
1 Geographical names in Australia are written with both Mac and Mc, witness the
MacDonnell Ranges and the McPherson Range, and in the suburbs of Canberra
both Macgregor and McKellar. The spelling in such names is often dictated by the
person being commemorated, and Governor Macquarie’s name has its exact echo
in a number of places. Macarthur was less fortunate in this: the Victorian town has
it right, but in northern Australia his name is respelled in the McArthur River and
Port McArthur. Note that the names of larger country towns such as Mackay and
Maclean are spelled out with Mac.
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