'after-dark' originates from Old English, specifically the words 'æfter' and 'deorc', where 'æfter' meant 'after' and 'deorc' meant 'dark'.

'after-dark' developed from the two-word phrase 'after dark' in Middle English and eventually became commonly hyphenated in modern English as 'after-dark' for adjectival use.

Initially, it meant 'after nightfall' in a simple, literal sense, but over time it evolved into its current adjectival and adverbial uses describing events or conditions 'occurring at night'.