leaf

Leaf comes from Old English lēaf, from Proto-West Germanic *laub, from Proto-Germanic *laubą, which traces back to Proto-Indo-European *lewbʰ-, meaning 'to cut off.'

The word has stayed remarkably close to its Old English form, lēaf, through Middle English lef into modern English leaf, always naming the same papery growth on plants.

It's cognate with German Laub ('leaves') and Swedish löv, and more distantly with Latin liber ('bast; book') and Russian луб (lub, 'bast') — words for bark and stripped plant material that share the old root sense of something cut or peeled away.