A name which is added to the Christian name, and which, in modern times, have become family names. 2. They are called surnames, because originally they were written over the name in judicial writings and contracts. They were and are still used for the purpose of distinguishing persons of the same name. They were taken from something attached to the persons assuming them, as John Carpenter, Joseph Black, Samuel Little See Name.
SURNAME
TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.