'lemon-flavored' is a modern English compound formed from 'lemon' + 'flavored'. 'lemon' originates from Old French 'limon' (and Late Latin 'lēmōnum'), ultimately from Arabic 'līmūn' (or Persian), referring to the citrus fruit; 'flavor' (US spelling 'flavor', UK 'flavour') comes from Old French and Latin roots related to taste (Latin 'flāvor', from 'flāvus' meaning 'yellow').

'lemon' entered English via Middle English from Old French 'limon' (itself from Arabic/Persian sources) and became the modern English 'lemon'. 'flavor' came into Middle English as 'flaur'/'flavour' from Old French, later stabilized in modern English as 'flavour' (UK) and 'flavor' (US); the compound 'lemon-flavored' developed by combining the noun and past-participial adjective to describe taste.

Individually, 'lemon' has long meant the citrus fruit and 'flavored' has meant 'given a taste of'; together the compound has consistently meant 'having the taste of lemon' with little shift in basic meaning since its formation.