horizon

Horizon comes from Middle English orisonte or orisoun, from Middle French horizon or horizonte, from Old French orisonte or orison, via Latin horizōn, from Ancient Greek ὁρίζων (horízōn), itself from ὅρος (hóros, 'boundary').

The word passed from Greek into Latin, then through Old and Middle French, picking up and losing letters along the way until Middle English settled on forms like orisonte and orisoun before English arrived at horizon.

Its root ὅρος (hóros) means 'boundary,' the same idea of a limit that the horizon marks between earth and sky.