'enfermedad' originates from Latin, specifically the word 'infirmitas', where 'in-' meant 'not' and 'firmus' meant 'strong'.

'enfermedad' changed from the Latin word 'infirmitas' to Vulgar Latin '*infirmitate', through Old Spanish forms such as 'enfermidad', and eventually became the modern Spanish word 'enfermedad'.

Initially, it meant 'lack of strength' or 'weakness', but over time it evolved into its current meaning of 'disease' or 'illness'.