Out of __ (from nowhere)

• Figuratively, whence some unexpected ideas
• The piece of ground in the outfield on the catcher's left
• Source of bizarre ideas, so to speak
• Where Why is, in "Who's on First?"
• Symbol of remoteness
• Site of Fenway Park's Green Monster
• Area patrolled by Jim Rice

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
left field \left` field"\, leftfield \left`field"\n. (Baseball) the part of the outfield on the catcher's or batter's left. Syn: left.

Wiktionary Word definitions in Wiktionary
a. From wikt:left field; off-the-wall