'propensity' originates from Latin, specifically the word 'propensitas,' where 'pro-' meant 'forward' and 'pendere' meant 'to hang.'

'propensitas' transformed into the French word 'propensité,' and eventually became the modern English word 'propensity' through Middle English.

Initially, it meant 'a leaning or inclination,' and over time it evolved into its current meaning of 'a natural tendency to behave in a particular way.'