Common First Name Variations for A Searching Program

Would anyone happen to know where I could find a list of common First Name variations? I’m working on a program which allows the user to add contacts (actually patients) to a system, and I want to try to prevent them from accidently creating duplicates as best as I can… I have a few already, such as Robert = Bob, Rob, Bobby, Robby; Michael = Mike, Mick, Mickey; etc… Thanks!