In a damnable way; deserving condemnation; terribly or frustratingly (used as an intensifier in modern usage).
From 'damnable' with the adverbial suffix -ly. This adverb transforms the adjective into a way of acting or being, originally with theological force but later generalized.
Interestingly, 'damnably' has evolved from a serious theological term meaning 'in a way deserving of damnation' to something more like 'annoyingly' in modern casual speech—a semantic softening over time!
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