A "Texas Leaguer" is a bloop that falls between an outfielder and an infielder for a hit.
Texas Leaguer dates back to 1901, when a rookie named Ollie Pickering made his debut for the Cleveland Blues (the franchise that would later become the Indians). Pickering had become a legend as a Minor Leaguer in the Texas League, and he was immediately placed atop Cleveland's lineup when he was called up -- he even holds the honor of taking the first at-bat in the history of the American League.
Pickering proceeded to have one of the most fortunate starts to his career imaginable, as his first seven plate appearances all resulted in bloop singles. His teammates decided to name the play after him, and it's stuck ever since.
Watch: Russell Martin picks up a single on a Texas Leaguer to right field.