The Homeric Greek word ἐπίουρος
Word ἐπίουρος
ě p i. uː r o ς
IPA epioːros
Meaning guardian, watcher, ward
Synonyms ἄλαλκε, ἐπίσκοπος, φύλαξ, μεδέων

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Iliad

Other words that might be of interest
μάρτυρος ‘witness’, ἐπιγιγνώσκω ‘look upon, witness, observe’, μάρτυς ‘witness’