Coke? What kind of nickname is that?
Warning: this isn't really a cool story... I just got tired of answering this question over and over. ^_^
As a student at RPI, I took an interest in the The RPI Players, mostly to get away from my weenie roommate.
At some point, I cleverly decided that I needed to be more involved with the goings-on at the Playhouse, (i.e. I wasn't close enough to failing out), so I volunteered to run our private Coke machines. (We did it ourselves so our prices would be reasonable for starving college students).
This service had a long and glorious tradition. Because of this history, and because the people stocking the machines were the only ones who had access to make change, I was commonly referred to as The Coke God. It's amazing how much respect you get when someone's dying for a cool refreshing beverage.
Later, due to a crossover in personnel (and my interests) between The RPI Players and EZ Chapter of Alpha Phi Omega, I decided to pledge the fraternity. Part of our fraternity culture was to take a nickname. Most brothers would call you by your nickname pretty much all the time. My big brother, the oft-maligned (and rightly so) Spike Abolafia, noted that due to an old (read: obsolete) computer program the chapter used, a nickname of six or less characters was ideal.
Based on the size restriction and my continued involvement with the soda machines, I shortened the Coke God to Coke... And it stuck. So much so, that I've had jobs where coworkerss referred to me as Coke, instead of Will. When I worked at Enron, I was introduced to Ken Lay during a company wide meet and greet as Coke by my manager. (Man, were the offices on the fiftieth floor nice.).