In Yiddish 'oy'ganes' means large protruding eyes as if in surprise. A form 'oy'genes' with stress on the first syllable exists and also a form 'oyga'nim'.
The Old High German word for 'eye' is 'ou'ga' in the nominative singular and 'ou'gun' or 'ougun' in the nominative plural. The Biblical Gothic (4th century) word is 'au'go' in the nominative singular and 'au'go:na' in the nominative plural. In Crimean Gothic from the 1500's the plural is 'oeghene.'
The Yiddish form resembles the Gothic form in having three syllables. However, the 'a' in the second syllable resembles the Old High German form. Both the Gothic and Old High German forms may have influenced Yiddish.