'inaptitude' originates from Latin via French, specifically the Latin word 'aptitudo' (through French 'inaptitude'), where the prefix 'in-' meant 'not' and 'aptus' meant 'fit' or 'suitable'.

'inaptitude' changed from the French word 'inaptitude' (from Medieval/Modern French) and ultimately stems from Latin 'aptitudo'; it entered English in its modern form as 'inaptitude'.

Initially, components of the word pointed to the idea of 'not fit or suitable' (from Latin roots), and over time it has come to be used primarily to mean 'lack of natural ability or aptitude'.