'flower-mad' is a compound formed from 'flower' + 'mad'. 'flower' originates from Old French 'flor' (from Latin 'flōs, flōris') meaning 'flower'; 'mad' originates from Old English 'gemǣd' meaning 'out of one's mind' or 'insane'.

'flower' passed into Middle English as 'flour'/'flower' from Old French and Latin roots; 'mad' comes from Old English 'gemǣd' and developed into Middle English 'mad(e)' and then modern English 'mad'. The compound 'flower-mad' is a modern English compound that follows the pattern of adjective compounds expressing strong liking or craze.

The individual components retained their basic meanings ('flower' = flower; 'mad' = mentally unbalanced), but in compounds 'mad' has extended to mean 'very enthusiastic about' (e.g., 'movie-mad', 'sport-mad'); thus 'flower-mad' means 'extremely enthusiastic about flowers' rather than clinically insane.