LinkedIn pored over the names of members to come up with the most common in various categories, notes Mashable. The results: 
 -  Male CEOs (in order): Peter, Bob, Jack, Bruce, Fred
-  Female CEOs: Deborah, Sally, Debra, Cynthia, Carolyn
-  Athletes: Ryan, Matt, Jessica, Matthew, Jason
-  Sales: Chip, Todd, Trey
-  Engineering: Rajesh, Jeremy, Andrew
-  Restaurant biz: Thierry, Philippe, Laurent
 Click for 
other categories or 
here for speculation on the use of nicknames.