come out of left field
To originate from a surprising or strange place. ("Left field" is the metaphorical origin of something uncommon, unpopular, or otherwise strange.) That suggestion certainly came out of left field! How did you come up with that one?
come out of left field
[for a problem or dilemma] to come from an unexpected place. (See also out of left field.) This new problem came out of left field. We were really surprised. Your remarks came out of left field. I can't understand your complaint.