If you have ancestors whose surnames begin with “Mc” and “Mac,” such as McKnitt and MacTavish, you may find them suspiciously absent in records even in places you are almost positive they should be appear. Sometimes the Mc or Mac may have been omitted by the person making the record or the record may have been misfiled under the second half of the name. Look in the records for both the full name and for the shortened version of the name. Of course this would also apply to O’Malley and other surname prefixes that could be separated. Learning to misspell and fracture your ancestors’ surnames can sometimes help you find those missing links.
-Taken from Ancestry.com