Meaning of ABACK in English

ABACK

adv. 1 archaic backwards, behind. 2 Naut. (of a sail) pressed against the mast by a head wind. take aback 1 surprise, disconcert (your request took me aback; I was greatly taken aback by the news). 2 (as taken aback) (of a ship) with the sails pressed against the mast by a head wind.

[ OE on b‘c (as A(2), BACK) ]

Concise Oxford English dictionary.      Краткий оксфордский словарь английского языка.