"That's not Latin!" - Lisa Simpson.
Dorcus Malorcus may not be Latin, but this is. Here are the Latin names of the 30 MLB teams, broken down by division. Big ups to Karen for assistance. And for putting up with my dorkness.
New York Urbani
Notes: for a lot of the animal names, I just used the scientific names. The Romans didn't know what a marlin was. "Metropolitan" is derived from Greek, and a Roman would have known what it meant, but I translated it into a Latin word. Philadelphienses doesn't mean anything but Philadelphians, and I'm not aware of any other meaning of "Phillies." The Expos could (should) find themselves as the Senatores, Nationales, or Cani (Grays).
St. Louis Cardinales
Notes: The Cubs seem to like Catuli, which works for any cute, fuzzy animal baby. Ursuli is more specific. The Russata was one of the chariot racing factions of Rome, so I used that instead of rubra or rosa or something. "Astros" comes from the Greek for "star," so there's Stellae. Dumb name.
Los Angeles Eludentes
San Diego Patres
San Francisco Gigantes
Boston Udones Russati
New York Iohannes
Tampa Bay Diaboli Raiae
Notes: Romans didn't really wear socks, and udo was the closest thing I could find. "Yankees" was tough; no one really knows where it comes from. The going theory is that it's the Dutch equivalent of "Johnny," so they're the Johns. Make your own joke. Diaboli Raiae is literally "rays of the devil." Diabolos, devil, is Greek for "slanderer." Is that the worst they could say about him?
Chicago Udones Albi
Kansas City Regales
Notes: For Cleveland, I chose to go with a word meaning "natives" rather than "people from India."
Notes: Two Greek words here, but they were both used by the Romans. Angelos in Greek meant nothing more than "messenger" until it picked up the Christian connotation (In modern English, Angelos means something entirely different). Nuntius is the Latin translation, but it never took on that meaning, so I kept Angeli. Athletici is Greek, too. "Rangers" is really difficult. Do you try to capture the police sense of the word? The army? Guy in charge of a forest? Pervagatus more or less means "one who ranges," so I went with that.
Try them with regunt (Cardinales regunt: Cardinals rule!) or sugunt (Iohannes sugunt: Yankees suck!).
UPDATE: The comments for this post are a cavalcade of edutainment. Seriously.