Its part of the culture of the game. It really originates with the players.

There have been some classic nicknames ...my favorites are:

Len Dykstra - 'Nails'

Bruce 'Eggs' Benedict

Al 'The Mad Hungarian' Hrabosky

The whole first letter of the first name second part of the last name nickname thing like 'A-Rod' etcetera also isnt as new a phenomena as you might think....long time Brave and Yankee outfielder Claudell Washington was known as C-dub forever, I'm sure there are others, that's just the first one that popped into my head.

Players don't just have nicknames for other players. They give them to their bats, gloves, hats, batting helmets, batting gloves, bases, umpires, shoes, stadiums, announcers, fans, uniforms......pretty much everything.

Baseball is a game of repetition and players (if you ask them) are constantly fighting boredom, nicknames are most likely a way of combatting that boredom.

...that said any nickname ending in a derivative of '-e' is a pretty half-assed effort.

**Edit: btw g' pa Babe Ruth's nick was the super creative 'The Babe'....the Bronx Bombers are of course a nick for the yank-ees, who have sometimes been know to play the phill-ies....