the.com/aback

The only place English still lets you be taken, as if surprise were a destination.

means To be caught suddenly off guard, startled or shocked by something unexpected.

from From the nautical phrase 'taken aback,' describing a ship's sails suddenly pressed flat against the mast by a shift in wind, stalling the vessel's forward motion. Before that, 'aback' simply meant 'backward' or 'toward the back' (a- + back), a plain directional word in Old English. Sailors gave it its jolt of alarm, and that's the only sense that survived into modern use — the directional meaning fell away, leaving just the shock.

origin
Old nautical term for wind slamming a sail backward
usage today
Survives almost solely in taken aback
literal sense
Originally meant backward or behind, not shocked
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