'disadvantageously' originates from the word 'disadvantageous,' which is derived from the prefix 'dis-' meaning 'not' or 'opposite of,' and 'advantageous,' which comes from 'advantage,' meaning 'benefit or gain.'

'disadvantageous' evolved from the Old French word 'desavantageux,' which was used in Middle English as 'disadvantageous,' eventually forming the adverb 'disadvantageously.'

Initially, it meant 'in a manner lacking advantage,' and this meaning has largely remained the same in modern usage.