You always come at me out of left field.

[HaraKiriBlade]

Partridge: "Amazes me how the old strings still pull. Yeah, there's a paper up there. A weekly. They looking for somebody, too. You interested, I'll give you the names I got. Want somebody to cover the shipping news. Guess it's right on the coast. Want somebody with maritime connections if possible. Quoyle, you got maritime connections?"
Quoyle: "My grandfather was a sealer."
partridge: "Jesus. You always come at me out of left field. Anyway, it works out, you got to handle... ...Give you the number."

It seems like an idiomatic expression to me. Could you tell me what it means, and possibly where the usage first came from? Much appreciated.
-HKB

[Ouisch]

Coming out of left field means that something is odd, unusual, unexpected or inexplicable. Something that slaps you upside the head and surprises you.

Parent: "I see you've been accepted to both Harvard and Yale. Which school have you decided to attend?"
Son: "I've decided that I'm going to spend the next year hiking across Turkey."
Parent: "What?! Well, that news certainly came out of left field."

"Left field" is a reference to baseball, although the actual origin of the phrase is in dispute. Many believe that it refers to early ballparks, where left field was often larger than right field and therefore was home to more lost balls and general confusion.

[2utopian]

I recognize The Shipping News.

"To come out of leftfield" means to say something unexpected.
It is a baseball expression.

• left field, as in "that insult really came out of left field" -- Unusual, unexpected, or irrational. AHDI dates this idiom back to the mid-1900s; it also states that the precise allusion is disputed, but a number of theories exist.[21] Rumored to originally describe fans who came to Yankee Stadium to see Babe Ruth (a right fielder) but who bought tickets for the wrong side of the field. Another legend is that the phrase originates from Chicago's old West Side Park which had a mental hospital located behind left field. Visiting players came to refer to something as odd to be 'out in left field.' The flaw in that story is that Cook County Hospital was behind third base, not left field.

"Depp's performance came out of left field in The Curse of the Black Pearl; nobody had ever thought of channeling Keith Richards and Pepé Le Pew before." — Kent Williams, "Pirates of the Caribbean: Dead Man's Chest" (review), Isthmus: The Daily Page, no date.