'before-breakfast' is a compound phrase formed from the adverb 'before' and the noun 'breakfast'. 'Before' originates from Old English 'beforan', where the prefix/root 'be-' contributed direction/positional sense and 'foran' meant 'in front (of)'. 'Breakfast' originates from the combination of 'break' + 'fast'.

'before' developed from Old English 'beforan' and remained a prepositional/adverbial word meaning 'in front of' or 'earlier than'; 'breakfast' came into English in Middle English as a compound of 'break' (from Old English 'brecan') and 'fast' (from Old English 'fæstan'), literally meaning 'to break the fast', and became the established term for the morning meal.

The components originally had the concrete senses 'in front of/earlier than' (before) and 'to end a fast' (break + fast); combined as 'before breakfast' the phrase has long meant 'prior to the morning meal' and has retained that meaning.