'unquestionably' originates from the word 'unquestionable', which is derived from the prefix 'un-' meaning 'not', and 'questionable', which comes from the Latin 'quaestionabilis', meaning 'able to be asked'.

'unquestionable' evolved from the Latin 'quaestionabilis' through Old French 'questionable', and eventually became the modern English word 'unquestionable'.

Initially, it meant 'not able to be questioned', and this meaning has largely remained the same in modern usage.