'unanswerably' originates from English, formed by the prefix 'un-' + the adjective 'answerable' + the adverbial suffix '-ly'. 'answer' comes from Old English 'andswaru' meaning 'a response', and the suffix '-able' (from Latin '-abilis' via Old French) meant 'capable of'.

'answer' came from Old English 'andswaru' > Middle English 'answere' > modern English 'answer'. 'answerable' was formed by combining 'answer' + '-able', and 'unanswerable' (with negative prefix 'un-') produced the adjective, which later took the adverbial suffix '-ly' to form 'unanswerably'.

Initially it meant 'not able to be answered or refuted' and over time has remained largely the same, used to indicate something conclusive or indisputable.