on-égan
This might be just a supplemental entry adding to an entry in the Main Volume.
In the OE text, the length is:indicated by acute accentsindicated by macronsnot indicated.
on-égan
AddHí onégdon þǽre ferelan slegas ictus ferulae pertimescebant, Gr. D. 229, 25. Heó náht næs hire onégende nec verita est, 279, 17. [Hí onégeæð formidabunt, Ps. Spl. T. 103, 8. Onégæn tabescere, 118, 139.]
This is a supplementary entry with editorial changes to an entry in the main volume of the dictionary. Look under the 'Possibly connected entries' below, or for the same headword in the list to the left.

A Combined List of Abbreviations.

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A Combined List of Abbreviations.