on-uppan
This might be just a supplemental entry adding to an entry in the Main Volume.
Related §§ in Wright's OE Grammar:
In the OE text, the length is:indicated by acute accentsindicated by macronsnot indicated.
on-uppan
I. AddÐá synfullan sceoldon bytlan onuppan his hrycge (supra dorsum suum ), Past. 153, 10. Ne cóm hé náuht onuppan ðǽm muntum, 399, 10. Þá sette Martinus his handa him onuppon, Hml. Th. ii. 510, 28. II. AddÆlfwold gesealde Eádwolde and his sunum .c. panæga anuppan eall ðis óðer, C. D. B. iii. 491, 16. v. þǽr-onuppan.
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A Combined List of Abbreviations.

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A Combined List of Abbreviations.