E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Aback.
I was taken aback—I was greatly astonished—taken by surprise—startled. It is a sea term. A ship is “taken aback” when the sails are suddenly carried by the wind back against the mast, instantly staying the ship’s progress—very dangerous in a strong gale.
