DictionaryRoot: lack
Middle English
lack
loss, failure, shame
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interjection
alack
uh-LAK/əˈlæk/
An old-fashioned cry of sorrow or regret.
Etymology
On Skeat’s account, this joins ah to lack in its older sense of loss, failure, or shame. Originally an expression of dissatisfaction, alack later became a cry of regret or unpleasant surprise.