'unflowered' originates from English, specifically formed from the negative prefix 'un-' (from Old English 'un-') combined with 'flower' (from Old English/Old French 'flor' < Latin 'flos, floris'), where 'un-' meant 'not' and 'flower' meant 'blossom or bloom'.

'flower' developed from Old English/Old French forms (e.g. Old English 'flēower', Old French 'flor') ultimately from Latin 'flos, floris'; the past-participial/adjectival suffix '-ed' made 'flowered' meaning 'having flowers', and the prefix 'un-' was later attached in English to form 'unflowered' meaning 'not flowered'.

Initially the roots denoted 'blossom' (flower); when combined as 'un-' + 'flowered' the meaning has been straightforwardly negative, i.e. 'not having flowers', a sense that has remained stable.