'free-flowering' originates from Modern English, specifically a compound of 'free' and 'flowering', where 'free' meant 'not restricted' and 'flowering' derived from 'flower' meaning 'to produce flowers'.

'free' comes from Old English 'frēo'; 'flower' comes via Old French 'flor' from Latin 'flos, floris', passed into Middle English as 'flour'/'flower', and eventually formed the participial 'flowering' used in compounds such as 'free-flowering'.

Initially, 'free' meant 'not restricted' and 'flowering' meant 'blossoming'; over time the compound came to be used specifically for plants that bloom profusely, i.e., 'producing many flowers' or 'blooming freely'.