I have a photocopy of a book from the 19th century called The Family of Cadenhead by William Cadenhead, an advocate (lawyer) from Scotland.
The book tells the early history of the Cadenhead family in Scotland, claiming that it first appeared in print in around 1560-1570.
According to the book, the name Cadenhead was given to people who were working land in Selkirkshire for the Pringle family. The land was at the head of a river or creek called Cadon Water, hence the surname.
At some point, I am going to publish the entire book on my personal Web site (http://www.prefect.com). A lot of it is very anecdotal, but it's still an interesting read for Cadenheads.