'inexplicability' is formed in English from the negative prefix 'in-' + 'explicable' + the noun-forming suffix '-ity'. 'Explicable' ultimately comes from Latin 'explicare' (see below); the prefix 'in-' comes from Latin meaning 'not'.

'Explicare' originates from Latin, where 'ex-' meant 'out' and 'plicare' meant 'to fold'. From Latin 'explicare' the sense passed into Medieval/Old French and then into Middle English as words like 'explicate' and 'explicable', and English formed 'inexplicable' by adding the negative prefix 'in-' and later the noun 'inexplicability' with '-ity'.

Originally related to the idea of 'unfolding' or 'making plain' (from Latin 'explicare'), the negative formation 'inexplicability' has come to mean 'the state of being not able to be explained' or 'resistance to explanation'.