'unbloomed' originates from English, specifically the prefix 'un-' (from Old English 'un-') meaning 'not', plus the word 'bloom' from Old English 'blōma'/'blōwan' meaning 'flower'/'to bloom'.

'unbloomed' changed from Middle English combinations such as 'unblome'/'unblomed' and eventually became the Modern English form 'unbloomed'.

Initially it meant 'not flowering' and over time this basic meaning has remained essentially unchanged into modern usage.