The New York Metropolitans
One of the more commonly known cases of a team abbreviating its name is the New York Metropolitans' official switch to "the Mets" in 1961. This one is perhaps the least surprising; Mets was shorter, less formal-sounding...and if you think about it, what exactly is a Metropolitan anyway.
The Cincinnati Redlegs
During the “Red Scare” of the 1950s, the Cincinnati Reds worried they would be associated with the threat of Communism and officially changed their name to the Cincinnati Redlegs. The Communist panic eventually subsided and the Reds name was restored after the 1958 season.
The Kansas City Communists
Up until 1953, this team’s name was a fan favorite. If you visited Kansas City on gameday, you'd likely hear loud, raucous chants of “go Commies!” and “we support the Communist cause!” (referring of course to the winning of baseball games). But, alas, widespread McCarthyist paranoia soon forced the Communists to change their name to the Kansas City Royals.
The Philadelphia Sillies
Few people realize it today but the word “silly” used to actually mean “intimidating and good at baseball”. However, as common usage of the word changed over time, Philadelphia was eventually forced to switch to the "Phillies", a name which most fans agree is foolish and lacking in common sense.
The Oakland Fucking A’s
Today’s baseball fan might find it hard to believe that a professional ball club would include the word “Fucking” in its name, but before the turn of the 20th century it was actually fairly commonplace. Oakland’s team, known less for its baseball and more for its lovemaking abilities, saw the name as an obvious and appropriate choice. They were later briefly renamed the Oakland Athletic Fuckers (after getting into great shape from fucking so much) but eventually shortened it to simply the "A’s" when women stopped having sex with baseball players in 1981.
The Detroit Tigerfuckers
New teams eventually began trying to one-up each other with more fearsome and aggressive-sounding names, which led to the founding of the infamous Detroit Tigerfuckers in 1894. Though by today's standards "Tigerfuckers" does seem somewhat crude and tasteless, the same argument could easily be made about the Pittsburgh Pirates. Or at least about their original name...
The Pittsburgh Tigerfucking Pirates
Pittsburgh's Management figured that the only image more intimidating than a sneering man fucking a tiger was a sneering pirate fucking a tiger. Though no one ever took issue with this name on a moral level (in fact it’s widely regarded as one of the best names in baseball history), they eventually had to shorten it during the Great Depression as "Tigerfucking" was very expensive to have sewn onto jerseys.
The Tigerfuck Orioles
In a desperate attempt to outdo both Pittsburgh and Detroit for toughest-sounding team name, Baltimore went as far as to officially change the name of their entire city to Tigerfuck, Maryland. Though the plan was initially a success, the later advent of Google led to potential tourists searching the city's name, becoming distracted by tiger sex photos and forgetting to book their trip. The city eventually changed back to Baltimore in 2007 but by then it was too late, they were poor.
The Cleveland Proud Indigenous People
This change occurred during a brief period in 1971 when it suddenly went out of fashion to reduce an entire race of people to grinning, red-faced, sports mascots. The nation quickly came around, however and the Cleveland Indians are still going strong to this day.