'defoliate' originates from Latin, specifically the word 'defoliare', where 'de-' meant 'off' or 'away' and 'folium' meant 'leaf'.

'defoliate' changed from the Late Latin/Old French word 'défolier' (from Latin 'defoliare') and eventually became the modern English word 'defoliate' via usage in Early Modern English.

Initially, it meant 'to strip or cause to lose leaves', and over time this core meaning has remained largely the same, though usage expanded to include chemical or tactical removal of foliage.