'invalidity' originates from Latin, specifically the word 'invaliditas,' where 'in-' meant 'not' and 'validus' meant 'strong or effective.'

'invaliditas' transformed into the Old French word 'invalidité,' and eventually became the modern English word 'invalidity' through Middle English.

Initially, it meant 'not strong or effective,' but over time it evolved into its current meaning of 'lacking legal or factual force or effect.'