'flower-crazy' originates from English, specifically the words 'flower' and 'crazy', where 'flower' meant 'blossom' (Old English flōwer) and 'crazy' meant 'mentally unwell' or 'mad'.

'flower' changed from Old English 'flōwer' through Middle English forms (e.g. 'flour') to modern English 'flower'; 'crazy' developed from the noun/verb 'craze' (17th century) and later the adjective 'crazy' (from the 17th–18th centuries). The compound 'flower-crazy' is a modern informal formation combining these two words to mean being 'mad' in the sense of very enthusiastic about flowers.

Initially 'crazy' conveyed 'mentally unwell' (or 'affected by a craze'), but over time it broadened in informal use to mean 'very enthusiastic about' when combined with nouns; thus 'flower-crazy' now means 'extremely fond of flowers'.