'leaf' originates from Old English, specifically the word 'lēaf', where the root meant 'leaf, blade (of a plant)'.

'leaf' changed from Old English 'lēaf', which came from Proto-Germanic '*laubą', and this evolved into the modern English word 'leaf'.

Initially, it meant 'a leaf or blade (of a plant)', and over time the core botanical meaning has remained while extended senses (such as a single page of a book) developed.