This is a well known surgical maxim but is not attributed to any particular surgeon I am afraid.
With modern scoring systems to predict who has a diseased appendix , with the advent of modern scanning as well as laparoscopy fewer and fewer healthy ones are being removed - so I think that particular statement is not just as true as it once was!
There have been hundreds of surgical luminaries over the years - it is easy to attribute a name to a new piece of surgical equipment or a new procedure but a phrase like this is just not possible.
I am sure that someone must have said it first but just who that was is not known!
Good luck with that!