Horizon

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late Middle English: via Old French from late Latin horizon, from Greek horizōn (kuklos) ‘limiting (circle)’.

wiktionary

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From Old French orizon, via Latin horizōn, from Ancient Greek ὁρίζων(horízōn), from ὅρος(hóros, “boundary”)

etymonline

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horizon (n.)

late 14c., orisoun, from Old French orizon (14c., Modern French horizon), earlier orizonte (13c.), from Latin horizontem (nominative horizon), from Greek horizon (kyklos) "bounding (circle)," from horizein "bound, limit, divide, separate," from horos "boundary, landmark, marking stones." The h- was restored in English 17c. in imitation of Latin. Old English used eaggemearc ("eye-mark") for "limit of view, horizon." The apparent horizon is distinguished from the celestial or astronomical horizon.