The LOOGY is the Left-Handed One Out Guy and is very real and very recent. This chart was adapted from data from baseball-reference.com using the Play Index feature (which expires tomorrow for me--guess I better do something about that):
Just to be clear, this is the percent of games in which a left-handed pitcher faced one batter. It could have been a save, a hold, a blown save or even a start where the pitcher was abducted by aliens after the first hitter and replaced. The idea of a one-batter pitcher appears to have taken hold in the mid-80's and really took off around 1990 when Tony LaRussa began to use Rick Honeycutt in that role.
So I decided to do a little research and my whole thesis got turned on its head. This is the list of all left-handed pitchers from around 1990 with 100 or more strict definition LOOGY guys--one hitter and gone, for whatever reason:
I'm sure I'm missing some pitchers, but I highly doubt it's very many. I began from a list from 2000 on and expanded it backward until I started running out of names, which happened far sooner than I expected. My games total won't square up exactly with baseball records because of the data I was using, but until I prepare this for my PhD thesis in advanced baseball metrics, I can live with that. Most of these players have a story--Jesse Orosco was a starting pitcher for years, Plesac a closer and Groom also a starter. The LOOGY is real, but perhaps not an entirely accurate name, but Left-handed One-INNING Guy (i.e., the LOIGY), while probably more accurate, doesn't really slip off the tongue smoothly.
Not all LOOGYs are the same:
1. In 229 of the LOOGY appearances, the one batter they faced hit into a double play--that's a LTOGY
2. On August 27th, 2007, Rafael Perez of the Indians entered the game in the 7th inning to face the Twins. Paul Byrd had given up a double to Michael Cuddyer and walked Jason Kubel, gifting Perez with runners on 1st and 2nd with no outs. Perez got Mike Redmond to hit into a triple play. Talk about getting your money's worth.