A second part of the study is working out where the Caddie surname comes from and this is one area that I have definitely struggled with.
I can find very few, if any references to Caddie on the surname websites - too rare. http://www.surnamedb.com/ have the following:
'Recorded as Cadde, Cade, Caddie, Caddy, Caddies and others, this unusual name has a number of possible sources, each with its own distinctive history and derivation'. It then went on to say it could be Anglo-Saxon for an Olde English personal name Cada meaning 'lump' and possibly applied to stout, plump people. The second option was Old French / early medieval as an occupational name for a cooper, from cade meaning cask or barrel. The third option was Middle English from Cade meaning a domestic animal.
This sounded to me that they were taking a bit of a guess and throwing anything into the descriptor that may in someway possible be Caddie'ish, particularly as it said it could be linked to Cadbury.
Moving on to http://www.searchforancestors.com/ a descriptor from Surnames of the United Kingdom, A Concise Etymological Dictionary by Henry Harrison in 1912. This said that it was a messenger or porter - Scottish Cadie, French Cadet - a younger brother; ultimately from the Latin Caput - head.
My personal view is that many versions seem to come back to the concept of 'fetching / carrying'; so if you think of a golf caddie as well as a the French cadet you have a 'gofer' - does this make it an occupational name? I am not sure but I don't think many others have any more of an idea.
Perhaps as my record study goes further back this will shed some light on it - otherwise not too sure where to look next.