'unreachability' originates from the English prefix 'un-' meaning 'not,' combined with 'reach,' which comes from Old English 'ræcan,' meaning 'to stretch out the hand,' and the suffix '-ability,' indicating a state or condition.

'unreachability' evolved from the combination of 'unreachable' and the suffix '-ity,' which was used to form nouns indicating a state or condition.

Initially, it meant 'the state of not being able to reach,' and this meaning has largely remained the same in modern usage.