In the US, there is a saying “Out of Left Field” which means strange, odd or unexpected. It is clear the origin can be traced back to baseball. But there are several explanations for the origin of the saying.
When it comes to the meaning “unexpected”, the following explanation makes a lot of sense. It refers to a play in which the ball is thrown from the area covered by the left fielder to either home plate or first base, surprising the runner.
The meaning “odd” or “strange” can be explained as follows. Before the Chicago Cubs moved into what is now Wrigley Field, the team played at the West Side Grounds. Behind left field there was a mental institution, part of the Cook County Hospital. Referring to the mental institution, Out of Left Field means odd, strange or even crazy as you are supposed to be in this mental institution when you are crazy.
A third explanation: The term “Out in Left Field” was also meant to describe people who were unknowing or crazy from a different baseball theme. In the 1920s, when Babe Ruth was in his prime, anybody sitting in the left field bleachers was regarded silly. Ruth, a left-handed power hitter, predominantly hit most of his home runs to right field. So those sitting in the left field bleachers were much less likely to catch a home run ball as they were sitting in the wrong part of the stadium.