I've heard that the prefix Mc-
in a person's name can be replaced by son of-
. For example: McArthur
can be understood as son of arthur
. I think the intention was to say what clan
you belonged to. So if you met Pidi
from the clan of the Cloud
, you could call him Pidi McCloud
. The later use in family names is pretty natural from there.
ooh! just found a node mentioning that: Irish Gaelic family names
Update: gleeme says: a similiar prefix Fitz- (e.g. as in "Fitzpatrick") means bastard son of while Mc- means legitimate son of.