Catch someone off guard

Meaning

Surprise someone when they are unprepared.

Usage

Used when news or questions arrive unexpectedly.

Origin & History

Origins and dates here are approximate summaries. Many idioms have disputed or unknown origins, and not every date has been checked against a historical dictionary, so treat specific dates and stories as a starting point rather than a citation.

Military image of attackers catching guard forces at a disadvantage.

Adapted into everyday speech for any unexpected moment.