spring on someone

Idioms  

1. Present or make known unexpectedly, as in They sprung the news of their engagement on the family last night. This idiom uses spring in the sense of “make a sudden move.” Mark Twain used it in Tom Sawyer (1876): “Old Mr. Jones is going to try to spring something on the people here tonight.”

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Example Sentences

Not really the sort of thing a person ought to spring on someone.

From New York Times