'powerlessly' originates from English derivation, formed from the adjective 'powerless' plus the adverbial suffix '-ly.' 'Powerless' combines 'power' with the suffix '-less,' where '-less' meant 'without.' The root 'power' comes via Anglo-Norman/Old French 'poeir/poeir' from Latin 'posse' meaning 'to be able.'

'poeir/poeir' in Old French (via Anglo-Norman) became Middle English 'power,' which yielded English 'powerless,' and with the suffix '-ly' formed the modern English adverb 'powerlessly'.

Initially, it meant “in a manner lacking power or ability,” and this sense has remained largely unchanged in modern usage.