'impenetrability' originates from Latin, specifically the word 'impenetrabilis,' where 'im-' meant 'not' and 'penetrabilis' meant 'able to be pierced.'

'impenetrabilis' transformed into the French word 'impenetrable,' and eventually became the modern English word 'impenetrability' through Middle English.

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