'deleterious' originates from Greek, specifically the word 'dēlētērios,' where 'dēlētēr' meant 'destroyer.'

'dēlētērios' transformed into the Latin word 'deleterius,' and eventually became the modern English word 'deleterious' through Middle English.

Initially, it meant 'destroyer,' but over time it evolved into its current meaning of 'causing harm or damage.'