Three True Outcomes
The Three True Outcomes are a walk, strikeout or home run. They are called this because the three supposedly are the only events that do not involve the defensive team (other than the pitcher and catcher). This ignores outfielders taking away potential homers at the wall, and inside-the-park home runs, and the like; however, over a career those events make up a very small portion of the total.
Prominent recent "TTO" players include Rob Deer, Jack Cust, Russell Branyan, Ryan Howard and Adam Dunn. Many all-time greats display this skill set as well, like Barry Bonds, Mark McGwire, and Jim Thome.
The term was reportedly coined by Christina Kahrl, a writer for the Baseball Prospectus blog. It was originally a bit of a joke - the site liked to use humorous names to describe some of the emerging trends of baseball in the late 1990s and early 2000s. The term LOOGY was another coinage from that period that took on greater life; however, the term "three true outcomes" quickly came into common usage as it reflected a reality no one could ignore.
- Diane Firstman: "From Usenet Joke to Baseball Flashpoint: The Growth of 'Three True Outcomes'", Baseball Research Journal, SABR, Vol. 47, Nr. 1 (spring 2018), pp. 29-37.