Probably the same as Atkins (which see).
Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.
There are approximately 292 people named Aitkin in the UK. That makes it the 13,070th most common surname overall. Out of every million people in the UK, approximately 5 are named Aitkin.
British Isles
England
English
Christian
English
Diminutive
Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.