Same or similar entry in other lexica (references at Photius omicron68 Theodoridis); the headword is evidently quoted from somewhere.
The thematic verb oi)gnu/w is a regularization of the athematic oi)/gnumi; earlier thematic forms occur with the stem oi)g-. For either athematic or thematic forms, the compound with a)n- is more frequent. See LSJ entry at web address 1, and other forms of this verb at omega 11, omega 38, omega 39.