If you guys have some time to kill here are two links that explain how every team got its nickname. Its a kinda interesting read.
http://pressbox.mlb.com/NASApp/mlb/pressbox/history/pb_history.jsp?team_id=mlb&content=nicknames_al
http://pressbox.mlb.com/NASApp/mlb/pressbox/history/pb_history.jsp?team_id=mlb&content=nicknames_nl