'before-lunch' is a modern compound formed from 'before' + 'lunch'. 'before' originates from Old English 'beforan', where the prefix 'be-' meant 'by/near' and 'foran' meant 'in front (of)'; 'lunch' originates as a shortened form of 'luncheon' (early 19th century), originally referring to a light meal at noon.

'before' changed from Old English 'beforan' into Middle English 'before' and eventually the modern English 'before'. 'lunch' developed from earlier forms such as 'nuncheon'/'nunchon' (a light snack at noon) to 'luncheon' and was later shortened to 'lunch', after which compounds and phrases like 'before lunch' (and the hyphenated 'before-lunch') became common.

Originally a literal combination meaning 'earlier than the midday meal'; over time the phrase has also been used as a compound adjective (e.g., a before-lunch meeting) as well as an adverbial time expression.