'before-dawn' originates from Modern English as a compound of 'before' and 'dawn'. 'Before' derives from Old English 'beforan', where the elements meant 'by/near' ('be-') and 'in front' ('foran'); 'dawn' derives from Old English 'dagung'/'dagian', where the root meant 'to become day'.

'before-dawn' changed from earlier Middle English/Old English phrases combining 'before' (beforan/bifor) and words for daybreak (dawen/dagung). Over time the two-word phrase 'before dawn' in Middle and Early Modern English became commonly used and is sometimes hyphenated in modern usage as 'before-dawn' for adjectival or attributive use.

Initially it referred straightforwardly to the time 'before daybreak'; the meaning has remained largely stable and continues to denote the period or events prior to sunrise.