This is a reference to the greek word βο-ῶπις or bo-opis, which is translated in different places as one of:
Homer uses it throughout his works; it is one of his Homeric Epithets. For example, he uses it in the Iliad, Book 1, lines 531-567:
‘Hera’ replied the father of men and gods, ‘do not expect to know all my thoughts: though you are my wife you would find it a burden. Whatever it is right for you to hear, no immortal, no human, shall know before you; but of what I plan without reference to the gods, make no question, do not ask.’
‘Dread son of Cronos,’ the ox-eyed queen replied, ‘what is this? I have never questioned you, nor asked: you have ever peace to think on what you wish. But now my heart fears silver-footed Thetis, daughter of the Old Man of the Sea, has swayed you; for she knelt by you at dawn and clasped your knees. Dare I imagine that you bowed to her, gave her a firm pledge of support for Achilles, and promised slaughter by the Greek ships?’
It is likely Homer chose to give her this nickname as her patron animal was the cow.