'after-breakfast' originates from English (a compound), specifically from the words 'after' and 'breakfast', where 'after' derives from Old English 'æfter' meaning 'following/behind' and 'breakfast' is formed from 'break' + 'fast' (Old English 'fæstan') meaning 'to break a period of fasting'.

'after-breakfast' developed from the two-word phrase 'after breakfast' used in Early Modern English; 'breakfast' itself comes from Middle English forms combining 'breken/break' and 'fast' (the meal that breaks the overnight fast), and the compound/hyphenated form arose in modern English usage to function adjectivally or adverbially.

Initially it referred specifically to the time 'following the breaking of the fast' (the meal that breaks a fast); over time it has generalized to mean simply 'occurring after breakfast' in everyday temporal and descriptive use.