There is clearly a prefix in names like McDonald, McChrystal,
O'Brian, O'Neal What does this Mc and O signify? Looks like
Donald, Chrystal, Brian, Neal are perfectly fine names on their
own so why is there a prefix The standard way to form a name
using a simple patronymic byname for men is: The standard way to
form a name using an Irish clan affiliation byname for men is:
Two common misconceptions are (1) that Mac means "son of" — it
actually means just "son", and the "of" comes from putting the
father's name into the possessive case; and (2) that Mc is Irish
while Mac is Scottish (or vice versa) — actually, Mc and Mac are
two ways to write the same thing, and both occur in names from
both countries. (What is true is that O' is almost exclusively
Irish; despite the romantic notions we have of Scottish clans,
they didn't use their clan affiliation in their names.) Edit: as
for why the prefix is used even though the prefix-less names
look perfectly fine on their own, this is basically Gaelic
grammar and thus ou