Word Study
alack
CIDE DICTIONARY
alack, interj. [Prob. from ah! lack! OE. lak loss, failure, misfortune. See Lack.].
An exclamation expressive of sorrow. Shak. [1913 Webster]
OXFORD DICTIONARY
alack, int. (also alack-a-day) archaic an expression of regret or surprise.
Etymology
prob. f. AH + LACK
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