WT:CFI: "For terms in extinct languages, one use in a contemporaneous source is the minimum, or one mention is adequate subject to the below requirements the community of editors for that language should maintain a list of materials deemed appropriate as the only sources for entries based on a single mention" (bolding adding)
So how about adding (OHG) glosses to that list which can be found at WT:About Old High German (the page doesn't have such a list yet)?
If (OHG) glosses isn't specific enough, here is a start:
Some random examples which these glosses could attest (from vol. 3, section entitled "DCCCCXXXI Vocabularius Libellus Sgalli."): "Rex cuninc Uir uuer Sapiens uuizzo Os mund Lingua zunga Cor herza Ros tau". Some normalisations could look like this: *kunink, *wer, *wizzo. -84.161.34.196 02:15, 26 September 2017 (UTC)
Are there any actual attestations before the 8th century? Runic inscriptions from the 6th and 7th century in southern Germany and so forth don't show any effects of the HG consonant shift afaik. (I think part of this book is about that, I've borrowed it from the library but not read it yet.) — Mnemosientje (t · c) 13:26, 5 November 2019 (UTC)
Early forms of OHG had sequences like -ea, -eo, -io in the second syllable, reflecting a Proto-Germanic -j- before the ending. This was later lost. Should lemmas reflect the earlier or the later form? Given that we already standardise on the later form th > d and hC- > C, I propose lemmatising at the later form in this instance too. —Rua (mew) 20:28, 27 November 2019 (UTC)
Noticed that the contents of tiuf and tiof were recently swapped so that the primary spelling is tiof. Noticed that some primary spellings use iu and some io, maybe based on etymology. I'm not familiar with OHG. Could someone write up the rules for this here for future reference? — Eru·tuon 19:36, 27 July 2021 (UTC)